When the mask enforcement was lowered in Australia I found myself wearing a mask where I didn't have to. It's such a small thing it wasn't worth taking it off while driving for a few minutes alone, or sitting somewhere away from people. I don't find people going further than necessary weird.

> a fully vaccinated adult

Being vaccinated isn't a perfect protection. I'd probably opt to wear a mask anyway if unvaccinated people around were forced to wear one. Wouldn't describe people not doing that as inconsiderate though.