... and two wheels move the soul. WTF does that mean? I shall try to explain.
OK, I have a theory. As a biological machine, man  has certain limitations, the principle one of which (apart from a stupid habit of repeating his  mistakes, yea, even unto the fifth generation) is an ability to move across the surface of the earth at no more than about 10 mph. Slow though this is, in comparison to leopards, horses, rabbits and the like, it is useful enough to have kept us alive for a good 100,000 years and counting. And using one's natural attributes to the full is always a bit of a thrill. Children run about for the fun of it. Running down a scree-slope, barely in control of your own feet, is a buzz. So, logically, anything which amplifies or extends one's own natural abilities is going to be a bigger buzz.
Take the low-tech stuff first. A toboggan allows you to descend a hill far faster than you could on your own feet, and is a whole barrel of laughs. A rope hanging from a tree lets you apparently whizz through the air without the limitation of ground contact. A see-saw lets you bounce into the air higher and faster than you could jump (and effortlessly cause someone else to do the same). No coincidence that these are all highly popular with children, who are always willing to give things a go and see if they are fun. We love to use things which extend our limited senses, like binoculars (whether looking at a distant hillside or the stars). Did you ever come across this? It's another wow, at least the first time you hear it.
And how much better when we invent the infernal combustion engine and make machines that will carry us at speeds and for distances previously undreamt-of. I think it's the travelling at speed and/or great distances with no real effort that flicks a switch in our primal brains that says "this is worth doing." More speed/power/distance; less energy expended - the primitive man that lives in all our heads is cheering at this point, thinking of more buffalo kills and a quicker getaway from predators.
So that's why boys like cars. Four wheels move the body, and that's a pretty good trick.
So why do some people like two wheels even better? We can start by getting rid of a the myth that bikes are more economical. They are not. This may have been true back in the days of three-speed gearboxes and optional-extra heaters (yes, reader, I can remember them both), when slow, rattly bikes did 100 mpg and even small family saloons struggled to do 25. But today a small diesel hatchback will achieve 60 mpg even driven with enthusiasm, and a big fast bike will struggle to get better than 40. My car (2-litre diesel estate) returns 42-50 mpg, depending on usage. My big bike (1300cc V4) gets an average of 38. If I want a cheap journey, I take the car. Road tax and insurance are substantially cheaper for a bike, but that is only a small proportion of running costs. The biggest and best bikes (if you are daft enough to buy them new) can cost as much as a medium-sized car.
Bikes have certain advantages, especially in traffic. Overtaking is a much more frequent affair, as the quick acceleration and smaller size mean that opportunities that are non-existent for a car are easy wins on a bike. Queues and slow-moving lines are usually bypassed by using the spare bits of road that the cars cannot untilise. You can park more-or-less anywhere there is a space.
And the disadvantages? Several.
Danger. I would be prepared to admit that riding a bike is more dangerous than driving a car, at least as far as the statistics tell us. No doubt, if you have an accident on a bike, the consequences are likely to be far more severe. I would also say that I am quite happy to ride a bike and feel quite safe doing so, for these reasons:
1. For an accident to hurt you, you have to have an accident in the first place. Defensive riding reduces the likelihood of an accident to a low and acceptable level. I have taken advanced training and I take my riding seriously. I ride with the attitude: "most of them haven't seen me, and those that have want to kill me." I have certain rules I never break: don't hoon round blind bends so fast you can't stop; never be the meat in someone else's sandwich, never trust a Volvo or a taxi , and so on.
2. Statistics can be very misleading things. Yes, more motorcyclists die or are seriously injured than car drivers, mile for mile. But this ignores the fact that there are two groups who between them account for the vast majority of bike accidents: youngsters, full of testosterone and inexperience, who have something to prove and believe they are immortal, and 40-something born-agains, who think the three years they spent riding a scooter between 17 and 20 makes them able to pick up a litre sportsbike at 45 and ride it to its limits. I don't fit into either of these groups. Apart from a 10-year break due to illness, I have been riding most of the time since I was 17 (that's 38 years, if you care to 'do the math'). I usually ride every day, in all weathers. I rarely ride in groups, I have nothing to prove, I don't drink and ride, and I hate hospital food. Although I enjoy riding fast and 'positively' (I hate the word 'aggressively') I don't take unnecessary risks and I am aware that there is always tomorrow. So, statistically, I am in possibly the lowest-risk group among bikers there is.
3. Risk is not an absolute. There is no such thing as a risk-free activity. Getting through life in one piece involves managing risks so that we can do the things we want, but keep the pain and injury to a minimum. So I concentrate on what I do; I have taken extra training; my bikes are well-maintained; I don't ride if I don't feel up to it; I keep my skills sharp by riding in all weathers and road conditions; I trust no-one but myself; I wear good protective clothing. (Notice that nowhere in there is a statement that I ride with my headlight on or dress up like a Christmas tree. Those are optional, according to circumstances, and long may they remain so.) I have the risk reduced to a level where I feel comfortable. If, after all that, I am killed while riding a motorbike, well ... at least I died doing something I loved and not in a care home after years of rectal cancer.
Weather. No getting away from it - the British weather is rubbish, and here in Wales it's rubbish squared. Cold, wet winters; warm, wet summers. On a bike, you are out there in it, and going along at such a speed that whatever is out there will be inside your clothes and next to your skin in no time flat. If you've never done a long ride home on a cold day with inadequate clothing, you don't know what cold is. Bone-gnawing, flesh-shrivelling cold. Cold that makes you want to drop your head onto the tank, curl up and go to sleep. And rain. Rain, rain, rain. Not just standing in a heavy shower, but standing in a downpour with the British Olympic Formation High-Pressure Hose team getting up close and personal with their lances in every nook and cranny. It must be awful, except that I love it. Rain, cold, wind - bring it on. I am a firm believer in Billy Connolly's statement: there is no bad weather, only the wrong clothes. I can remember when there was no such thing as waterproof motorcycle clothing - only points on the cost/wetness curve. Nowadays, it is possible to be completely warm and dry on a bike, in any weather. The only conditions that make me want to take the car are ice and snow (for obvious falling-over reasons) and fog. The feeling of vulnerability on a bike in thick fog is most unpleasant, and the risk of something nasty happening is very real. But for the other 360 days in the year, it's the bike, every time.
None of which answers the question I started with - why a bike rather than a car? I've argued about why we like to travel, and I've argued against the perceived negatives of riding a bike. But I haven't touched on the joy of two wheels, why bikes are better than cars, and why I will always choose to make a journey on two wheels unless circumstances demand a tin box. I've wittered on so long I will have to leave that to another post.
 The species, not the bloke. If I refer to man, I mean mankind, just people, OK? If I wanted the term to be inclusive, I would say 'person', and that would sound stupid, so man it is.
 His includes the female of the species too. As my old English teacher used to say, "the male embraces the female, ha ha." If that makes anyone feel excluded or diminished in any way, I'm sorry, but I refuse to use the gender-neutral but horribly ungrammatical they.
 And if you find a Volvo taxi - well, just get the hell out.