Here is something I've noticed among drivers: leaving a full car-length between yourself and the car ahead of you when stopped at a red light.
Maintaining proper distance from other cars while riding down the road is important. It's wise to leave plenty of stopping distance. I think it makes sense to keep your distance when in stop-and-go traffic. But, while waiting at a traffic light?
It's not usually a major problem for me, of course. There are times when I'm blocked from entering the turning lane by the car that waits a car-length back. That has cost me a traffic-light cycle of waiting time more than once. But I am patient; I can handle this.