Yes I'd hate to pass it on to others but I have yet to wear one. I barely go to stores and stay away from everyone at least 6 feet. My understanding was that as long as you can maintain social distance then mask wasn't that important. Thought it was mainly for people that have to crowd together like in public transportation. Here in Texas a majority still wear them in stores but more people are starting not to. Yes I know I'm terrible person not wearing one but I try to stick to nose breathing only and barely any talking while in gas station or store.
The current advice here is to where one in places where social distancing is a challenge. Like you said, public transport, crowded stores. No talking and breathing through your nose also reduces the spread as much as a face mask would. The smallest aerosol particles get through the mask anyway (and can survive up to 4 hours drifting around in the air). But you need more exposure than a couple particles for the infection to have a chance to take hold. It's a numbers game hence the 2 meter distance. The more chance the virus has to disperse in the air the less dangerous it gets. However if it keeps recirculating through air conditioning in a confined space, risk of infection goes up.
Masks are mostly effective to stop spread through talking, coughing, sneezing.
Touch is a bigger factor to catch it, so always wash your hands after touching things, before touching your face or taking the mask off. And again after taking the mask off in case anything stuck to it.
And then you have to be careful with lunatics around. They caught a guy here at Walmart, opening shampoo bottles and spitting in each one of them, then putting them back on the shelf. They took all the shampoo off. (The virus probably dies in the shampoo anyway, but really, some people...) Hence I'm not taking any chances with stuff coming in the house either.
Always good to wash your hands again after handling anything coming from outside, taken back home etc. Plastic 3 to 7 days....