the point with wearing masks at all times in public space is you don't have to take it off and put it on all the time you pass around someone, you never know when there will be someone around you and even if you are alone you can still cough the virus on surfaces where it can survive at least for few hours touched by other people

I agree it's quite pointless for healthy not coughing person, but it's just easier to order everyone to wear them than checking one by one who is sick and who is not.

not sure how is mask wasted, if it's cloth mask you can just microwave it or boil it, if it's medical mask you can just leave it on sunny surface until it's for sure clean again or microwave it, same applies to respirator