There are two places near me where it really annoys me. One is pulling out at the t-junction on the main road and it is usually busy. You sit waiting for a gap, but there is a car coming. Then it slows down and you are tempted but if it is going straight on you will cause an accident. Eventually it turns in and half way though the turn the indicators click on. People don't know that an indicator is to indicate what you are about to do, not show what you are doing when it is obvious anyway.
Every time that happens, I could have been out but by the time you know they are not going to be a problem for you, there is other traffic.
The other is a t-junction where I cross the road to the local field with the dog. Almost everyone who comes up and turns right down the road just before I cross, doesn't bother indicating. You stand and wait looking right at them as they come up the road, and in they turn. I must see that at least 4 mornings per week.