Sometimes I wonder whether going excessively slow around corners is a symptom of people pushing their steering wheel from the side opposite the direction of the curve instead of pulling it from the same side into the curve. Just a hunch, but doing the latter usually feels like I have more control.

I don't know about that. But what I usually observe is that many people tend to veer off in the next lane in the direction of the turn (even if it's a lane for traffic going the opposite way!) if there is one. But if there isn't (right turn, they're in the rightmost lane), they'll tend to leave quite a lot of space between the car and the shoulder.

So I'd say these people have a hard time figuring out the space on the road their car takes. I can only imagine this worsens with larger cars and less visibility.