I believe this study, and I believe that a vast majority of poor people would spend the money reasonably, but I do think there is a small subset of poor people who will be "perpetually poor." They have little/no financial literacy, they'll spend the money in a fairly frivolous way, and I think giving them raw cash instead of something more or less boxed-in like food stamps can lead to a lot of issues.
I think a lot of people see the majority of poor people acting extremely responsibly and just assume that irresponsible people don't exist. The problem is that they do, even if they are a minority, and we do need to help them too.
I am much more open to a UBI if we have it in addition to our current welfare programs, a lot of people would definitely benefit from having a guaranteed safety net, but I think we shouldn't forget that "the majority" doesn't mean "everyone".
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EDIT: It appears that I didn't explain myself very well. I'm not trying to give a Reagan-esque welfare-queen thing, specifically because I actually would prefer we increase welfare/safety-net spending instead of reducing it.
I'm not trying to shift a burden of blame on anyone, I'm sure there are socioeconomic reasons to why some people lack financial literacy.
I guess what I'm trying to say (and this may come off as hyperbolic) is that I get a little bit of a social-darwinism vibe when people act like people mismanaging money don't need to be addressed in topics of UBI.
Obviously not everyone says this, but there is at least a subset of people who pretend that nearly everyone, given enough money, is this hyper-rational actor who always spends their money efficiently and that we shouldn't worry about the 1% of people who aren't.
Even if it is just 1%, these are still humans, these are still people we should take care of, and these are people that depend on the current level of social safety nets.