Selfishness, stupidity, impatience.
I drove the same stretch of road twice today, and both times a dickhead in a larger than necessary vehicle was aggressively driving behind me, and as soon as a second lane started to open up they zoomed around me. The second one didn't even wait for the dotted lines; he went around as soon as there was enough space.
In both cases they immediately got stuck at the same red light, and in both cases I was about two seconds away from moving into the right turn lane when that opened up. The only result of driving like that was raising their own stress levels (and mine a tiny bit.)