Originally Posted by mnemia

That may be the case for some of them, but for many I think it's just incompetence. They just don't think you're worth paying much attention to, and so they stop thinking about you as soon as they pass. Out of sight, out of mind. A lot of motorists really suck at driving, and use lazy shortcuts in their driving instead of actually paying attention or being careful. They'll assume, for example, that things that are behind them are not going to affect them. Or they categorize bicycles and pedestrians as stationary objects in their minds. The cell phone epidemic doesn't help with any of this, obviously, since it divides their attention even more and makes it harder for them to pay attention to everything around them.