My guess would be that people draw left to right, and also start drawing the part that is simplest. If you look at some of the drawings it seems that people get

My guess would be that people draw left to right, and also start drawing the part that is simplest. If you look at some of the drawings it seems that people get confused about how the gears and the rear wheel connect to the rest of the bike, while the front wheel and handlebars are more often correct.