Chains have very real problems and frustrations that crop up often- when used on motorcycles. When it comes to bicycles though, I suspect it is the other problem with chains that drives people;
They aren't pretty, symmetric, or aesthetically pleasing. Strangely, this is apparently a very serious problem for many people.
Note: All the problems with a motorcycle chain apply to a bicycle chain, but motorcycles travel massively greater distances, at higher rates of speed, through tougher environments, while transmitting anywhere from 20-400x as much power as a bicycle chain.