A group is a collection of individuals. Anecdotes != data and whatnot, but by my observations people don’t always make purely rational economic decisions, so if you were going to a see people quitting over UBI you’d already see it.

Of course this hypothesis is as based in reality as yours, so the only thing we can do is try and find out.

With your caveat of "Anectodes != data and whatnot, but by my observations", people don't make rational food decisions when given free money. They tend to spend on snacks and sugar, not on veggies. Unless discipline is enforced, free money is a disaster.

Are you also going to have "free health care" with UBI ? That would be cataclysmic as you would need to also give free diabetic and obesity treatments until end of lifespan.