I think we're still waiting on data on how much virus gets in the air from normal breathing, but it seems plausible that it's not insignificant and may be reduced drastically by you wearing a mask. If you're leaving a cloud of virus in your path, putting on a mask for only the few seconds you're passing someone isn't going to do anything about the cloud of virus you could possibly be leaving in your wake.
> If they're not within 6' of another person; there is nothing inherently bad about being outside.
6ft is a bit of an arbitrary number that's easy to remember, but people are treating it like it's some magic shield. Time spent in proximity presumably plays a factor as well. Walking quickly past someone at 3ft away is probably a lot safer than standing 10ft away from someone and talking for ten minutes. Being outside certainly should help, but in a place with a high concentration of people with the virus I would not consider it a safe activity.