It's just hygiene theater to make people feel better. 95% of time when I see masks in a situation that isn't particularly risky (outdoors), it's not an N95. People do it because it makes them feel safer and to virtue signal.
What's bizarre is that it's rare for public health officials to care, either. It makes me think they're actually very effective (which I doubt with delta), they want to people to feel safe to keep the economy running, or they're worried about how much more contagious it could get facing a real obstacle.
As for the hard lockdown, I think we're past the point of that being a theoretical option. Looking to Australia, it's still spreading. There's a level of contagiousness where the minimum amount of interaction is still to much to stop the spread. We'll see what happens in New Zealand.
You're right about the national scale for everywhere other than Singapore. There are just too many people too spread out to actually enforce it. Borders are too porous, and enough people are onboard with letting it spread that this option isn't practically or politically viable.