I finally got around to fixing my bike ahead of the Norcross Scurry on Saturday and in the process I was thinking about the weirdness of parts on bikes that are disposable. I was replacing the rear derailleur and chain. Isn't it weird that what is a bicycle's drive shaft breaks with such frequency? On my mountain bikes, it seems to be about once per year or so that I replace a chain. If drive shafts on cars with that frequency, there'd be incredible number of cars broken down on the side of road. Same thing with tubes: if cars got flat tires as frequently as bikes, there'd be dead cars littering the sides of roads everywhere.
To that end, I wonder (because I'm ignorant) about motorcycles. They're to some extent big bikes with motors, do they break down as much as bikes?
I suppose cars do have mechanical problems fairly regularly, but the problems aren't as inhibiting to movement as they are on bikes. Well, mostly I'm wondering if chain drive motorcycles break chains very often. There's a lot more torque on those chains than on bikes.
Further, why do so many bike parts seem so much more disposable than parts on other modes of transportation. Are bikes just built to break down?