The current recommendation is to wear a mask outside if you cannot maintain 2 metres physical distance. So, most of the time, no need.
Back to first principles. Viruses pass from one person to another by an infected person breathing it out and another person breathing it in. If there is ample dilution, that's exceptionally unlikely to happen. Ample dilution happens outside unless you are crowded together. Ample dilution happens inside if there is good ventilation relative to the number of people present. If you're spending extended periods of time too close to an infected person without adequate dilution, you're going to get exposed, and the amount of virus that person emits is affected by speaking, singing, coughing, sneezing etc and whether they have a mask on (and how good that mask is). That's the thing you fundamentally have to avoid.
But lots of people can't think through that ... hence ... rules ... and shutdowns of certain activities that are prone to leading to those circumstances existing.
But you can't shut everything down ... so there's a risk calculation that has to be done.
I had a dentist appointment today. Unavoidable. Had to be done. And my dentist is in Peel Region. They're doing the best they can. After basic X-ray diagnosis revealed that the situation need not be taken care of right this moment (for the moment, I can deal with it) we agreed to revisit this if it either gets worse to the point that I can't deal with it, or after the coronavirus settles down ... at the moment, I don't want to spend any more time in that situation than I absolutely have to. Risk management.