I think a lot of people don’t even know if their skills are bad. Just yesterday I was making a left turn and watched the car next to me, which was also turning left, do the typical poorly done left turn.
It’s a six lane road turning onto a six lane road (not that it matters that much how big it was, because I see this mistake on smaller roads too). There are two left turning lanes. I’m in the US, so we drive on the right. We have a turning arrow, so we can drive right through the intersection without slowing for opposing traffic. The guy next to me does the typical turning too early while going through the intersection. Why do so many people do that? It explains why municipalities sometimes draw the lane markings through the intersection. Left turns are, or should be, close to 90 degree angles. If you turn too soon it’s easy to wind up swinging out into the next lane. You have to do a correction as you get onto the new road when you already are gaining speed.
So many people seem unable to stay in their lanes when turning. Not only on left turns, right turns too, but I think with the left turn many people can’t do the turn correctly, they don’t know how. The right turn they are just being sloppy. It’s ok in places not very congested, but in very busy cities you need to stay in your lane so traffic can keep moving as much as possible. Where I grew up if two lanes were turning left, let’s say I was traveling east, turning north, onto three lanes, the outer lane had someone traveling west turning north into that third lane. You had to stay in your lanes through turns. Do you stay in your lane? Most cities you can’t count on drivers doing it.
I have a girlfriend who openly says she is a bad driver and that’s why she likes to drive really big SUV’s. I told her the bigger vehicle probably contributed to her “frequent” accidents. Too many blind spots on that thing.