So much of the justification for ignoring precautions about COVID is all-or-nothing thinking.
Just because you inhale one COVID virus particle doesn’t mean you’ll get COVID. Your precautions won’t be perfect, but that doesn’t mean they are useless. The more particles you inhale, the more chance of getting it, and every particle you block lowers your chances of getting it. Even partial precautions help. It’s not all or nothing. It’s degrees of risk.