Well what I am thinking more is that without that pressure people will just screw off and do meaningless things that please themselves in the short term but add up to nothing and leave them feeling hollow and empty in the long term. There's the obvious concern that it might just be eating sweets or jerking off but I've seen many people waste time on 'creative' projects which go nowhere because they aren't trying to satisfy a need anybody else has or bothering to contextualize what they want to do with what other people have done.
Like I think businesses only provide good products and services because they have competition and when they don't, they don't.
You can make the case that UBI will lead to human flourishing and probably some people actually will flourish in that case while others will languish.