People in cars are just so impatient.
Recent experiences: Paused at a junction in my car to allow some pedestrians to finish crossing (already in the road so would have run them over if I'd kept going). Person behind starts hooting frantically. That's happened twice in the last month.
Stopped on my bike to let a mother duck and some ducklings across (again they were halfway across when I came round the corner so I would have run them over). Cue driver behind hooting and shouting abuse. (Road with a 20 mph)
Stopped on my bike to let a wheelchair user cross at a zebra crossing. Driver behind overtook me, went through the zebra and almost hit the wheelchair user who was in the road by then (don't think he even saw the person crossing, just saw a stopped bike and though MUST OVERTAKE)
Stopped on my bike at a red light. It had been red for about 10 s when a car overtook and went straight through (don't think he even saw the traffic light, just saw a stopped bike and though MUST OVERTAKE)
Crossed at a zebra crossing on foot - got abuse from a driver who came hurtling round the corner far too fast and struggled to stop in time.
In my car, I indicate right to pull into my drive. The car has a poor turning circle and I need to pull out to the left a bit to make the turn. Several times people have tried to overtake on the right even though I am indicating right, then hooted at me when I start to turn. This is also a 20 mph zone. The first couple of times I thought my indicators weren't working. They were.
As a cyclist, close passes due to impatience happen on a daily basis.
As a driver, slow driving can sometimes be a little annoying - but it doesn't come close to all the dangerous things that impatient drivers do. They always seem to think they know best, not imagining that there is a perfectly good reason why someone is slowing down/stopping