The point from most of the comments seems to be, if unemployment is enough to live on and the alternative is a job you don't particularly want to do, then there's no incentive to do the job you don't want to do?

If UBI just replaces unemployment, how does that calculation change? You still have enough money to live on you still don't want to do the job being offered?

Unless UBI is sufficiently low that you need a job to survive, in which case... is it UBI?

Nothing says people aren't willing to work if they pay is good enough. Unemployment is effectively a 90% tax rate in the bottom bracket, making work pointless.