I'm talking about gutters on the street, beside the kerb. I thought this was implied after I said "keeping your block clean by sweeping and mulching". You routinely see older people in Asia sweeping and raking a communal area if you get up early to walk. There's a (probably obsessive-compulsive) 60 yo guy a few houses down from me in Australia who might've retired early and now goes around raking verges and cleaning the footpath/gutters meticulously. Near my office, there's a woman who bakes bread for the joy of it and sells it at-cost via an honour-box in a sidestreet. She also turns verges and front yards (with owners' permissions) into a community vegetable garden. If others were given an opportunity equivalent to early retirement, these sorts of things might be more common.

As for why: for purpose, for praise, for community, for mental health, for trade/contribution, for skill building, etc. Loads of examples of this already. Maybe none of these things are attractive to you but I don't think that's universal.

Like I said, it's just trying to add to the default UBI, not getting everyone volunteering in their community or else.