I actually saw it a few times because my father would make note of it beforehand.

Guy going in parallel to the road on the sidewalk, looking sideways and gunning it to make it before the car makes a turn.

Or worse: also going in parallel, but making a left turn onto the road without looking.

Looking sideways from a bicycle is not something you do for fun, it's a way to see what drivers are up to. Especially when they drive up beside you it's pretty hard to know what they will do.