Drunk on power? I imagine most don't want to ask people to wear masks as they will know it could lead to confrontation when that kind of thing is something they want to avoid and is not part of their job. I have watched a number of videos online of maskless people recording confrontations with shop staff, police etc.. Then when you look at their profiles, they are often, let's say, questionable characters. May be for some it appears a link between unable to wear a mask and being an arsehole?
We should not forget that the bigger issue here are selfish people, some of them lying, who could be spreading a virus rather than a shop worker asking someone to wear a mask.