Good masks do make a difference. A flimsy cloth one that still allows you to blow out a candle, though, doesn't.
But most transmission is done indoors, between people who spend time together and with poor ventilation.
I wear a mask outdoors, to be on the safe side, if in a crowd, with a few people at a bus stop, or similar.
But I don't think mandatory outdoor masks are useful or even a good policy. It leads to mask fatigue and people will be more likely to have risky behaviours.
BTW
" I comply with shops and restaurants (although questions how wearing a mask when walking 5 metres to a table then taking it off makes any sense)"
You're not supposed to take the mask off when you sit. Just when you eat. If you're at the table, just talking, it's best to wear a mask. Even with household members, you're still doing a favour to the restaurant workers and other people around.
There's increasing evidence of aerosol transmission, and aerosols linger in the air and move around with air currents.
Most of the current guidelines are for droplet transmission and probably not enough to stop the spreading.