Drives me absolutely crazy. Am so with you OP.
Staff in my local costa are ALL wearing it beneath nose. One woman told me somewhat patronisingly to please fill in track and trace. Now, I KNOW she HAS to tell me and if she comes across as patronising I am absolutely certain she didn't mean to but I snapped and said, "I'll fill in track and trace if you wear your mask properly."
Believe it or not, neither her nor the barrista felt embarrassed and started wearing them right. I won't be rushing back there.
I'm not even particularly paranoid. It's just that I think if your'e going to do it, do it properly otherwise don't bother. And they are preparing f888ing food!!!