UBI gives people control over their own money. Food stamps for example gives poor people a disproportionally large food budget which studies has shown makes them fat. People who are equally poor but aren't on food stamps are healthier than those who get it, even though their purchasing power increased.

So only reason to give them food stamps instead of just giving them money is to feed money into grocery stores and to create government bureaucracy jobs. If you scrapped the entire program and just gave people money poor people would be healthier, the government would be leaner and the poorer would have more money to spend on stuff they need.