It seems pretty complex to design a version of a lax unemployment policy that eliminates steep cliffs that might disincentivize working, is fair, and also doesn't let anybody slip through the cracks. How do you handle someone quitting voluntarily, or retiring early, or starting their own business which doesn't pay them yet, or only paying themselves a small amount, or working a part-time job on the side while focusing on something else, etc.

The income tax code already exists and has to solve some of these problems, so it seems easier to give everyone the money and then tax it back from the highest earners later (or implement it as a negative income tax, but that has its own hurdles as well, i.e. imagine a homeless person needing to wait until tax season and then getting paid for the whole year, it would be a big hurdle and they'd still need other assistance programs the rest of the year if they didn't budget the money well enough).