There's a lot of evidence of people choosing not to work if welfare provides a living that's comfortable for their tastes. I have a neighbor (in his forties) that is among that group, he's quite content watching tv, playing xbox and listening to music all day and getting drunk every few days, which he can afford on welfare, and he has a large-ish flat (same one I do), all paid for.

I wouldn't want to live that way, you probably wouldn't either. But he would and he is. UBI would certainly not be lower than today's welfare programs, and it wouldn't even have the modicum of incentive ("you must be looking for work" vs unconditional), so how would it not have a built-in disincentive to work on people that are fine with living their lives that way?