A decent amount of it is unintentional I suspect. Subconcious fiddling, poor feeling / awareness of slipping masks... a gentle reminder that "your mask has slipped a bit" can do wonders.
Seen a guy on the street taking off mask to do giant sneeze, put it back on afterwards promptly. His wife facepalmed. To his defence he’d probably have to wear juicy mask if he didn’t do it.
1) you wouldn’t (shouldn’t?) go around with your dick hanging out of your trousers, so why would you do the same with your nose and your mask
2) you’re a dick if you do this