There's also a social tipping point sort of thing that happens, and fines help with that. When hardly anyone is wearing a mask you feel a bit weird or silly.

There's also a social tipping point sort of thing that happens, and fines help with that. When hardly anyone is wearing a mask you feel a bit weird or silly. When half the people are wearing masks you look at the people who are and aren't and can't help but wonder which side is your in-group. When fines are enforced, everyone has an "excuse" to wear a mask. Darn fines. Then, when everyone is wearing a mask you feel naked if you don't have one. Only the seriously anti-social will defect.