I was a biker until recently (when I had to sell my BMW R1100S). At heart, I still am, and I can't wait to get another one.
It's like all hobby things - it's good to meet people with similar interests. Riding a bike is exhillarating - even at slower speeds.
People also do customise their bikes - even sports bikes. When you meet someone for a ride, it's quite natural to look at what they're riding.
And the police do do things about it. Believe me - become a biker and you'll soon feel victimised. How often do you get police stopping cars at car parks checking for tax, illegal number plates, loud exhausts etc? Not very often. You get a recognised bike event, and you can guarantee there will be the over zealous plod there.
And cars do do this too. Have you not seen the boy racer GTI clubs, with their loud music, even louder exhausts, and often very irresponsible driving?
Sure - bikes can be ridden poorly, but in my experience, car drivers are worse in towns where injuring pedestrians is more likely.
There. Minor rant over.