At character level 2-5 it's pretty rare, say one character out of a party of 5-7.
At character levels 6-11, it's uncommon, say 2-3 characters out of a party of 5-7.
At character levels 12+, my sample size is smaller. For games that started at high level it seemed a lot more common then games growing to that level. Actually, that may have been true even at the lower levels, that a replacement character or new player starting at a higher level was more likely.
I myself like single level characters, and will likely stay that way until I'm at a level where I've got all my "major goodies". Since I've never actually seen a 5e camapaign go to 20th at that point I don't mind missing out on a mythical capstone and instead can multiclass. Though I will multiclass even from 2nd if I have a concept I'm going for that isn't well realized mechanically by a single class, but it that case I try not to hit the class-level-5-power-bump too late, say 7th at worst.