Because:
A) you have to spend 10mins zipping yourself up in a leather suit every time you go out.
Not true. I don't own a set of leathers.
B) you're exposed to the elements. So you're either sweaty and gross or wet and freezing.
Mmm, so so. I get full of dirt and don't mind.
C) you're at risk of being squashed by cars, tumbling into fences, slipping over on manhole covers, potholes etc.
There are risks to anyone who's near a road, pedestrians, cyclists etc.
D) you have to be concentrating at all times to maintain your balance.
Really! Just lol
E) no stereo.
You could have a MP3 player etc, but I prefer to listen to the engine.
F) no storage space, you can't buy anything while you're out.
Some have storage, or you could just put stuff in a back pack.
G) even having one passenger is a complete pain.
Not on all bikes.
H) ruins your hair by the time you get to your destination.
Most are bald. lol
I) most sports cars are plenty fast enough for most roads. Unsure why anyone needs such straight line acceleration that a bike has.
It's not all about acceleration and top speed. Your a much bigger part of the machine, you feel the suspension loading/unloading as you flip from left to right, brake and squeeze the power on.
You can feel the road surface changing, the tire squiggling the smell of the things around you, the sound and vibration of the engine etc. So much information to feed your senses.
Get home, kick back with a cold one and remember the day with a huge grin on your face.
J) they all sound like hair driers compared to any larger engined car.