A shorter term problem
Is that with UBI, many more people might decide that doing some jobs wasn't worth the hassle, compared to doing something else with their time, and living off UBI. I'm not talking about the feckless idle that all societies have (they're already on benefits, or "NEETs), I'm talking specifically about the quite large number of:
- people on crappy zero hours contracts,
- people doing horrible minimum wage jobs or low paid shift work,
- people simply doing unthanked and sometimes nasty jobs, eg prison officers, traffic wardens
- people simply working for really shit employers, like JD Sports, or Amazon.
There's a lot of different consequences if any proportion of those people throw in the towel, with few good outcomes or easy resolutions.