The fundamental problem with UBI is that if it is enough to live on (even if it's a crummy life), then who is going to pick the strawberries? The ugly truth is our society is built on top of people doing absolute shit jobs for insulting pay.

If someone needs that money to eat they'll do the job, but if you're asking them to wreck their body in inhumane conditions in order to have slightly more spending money then they're going to say no. Even if their living conditions are lousy it's better than bending over in the mud under the boiling sun while a slave driver yells at them all day long.