For example, look at Social Security: as the population ages, fewer people are working while more people are receiving. Of course, the Fed can literally create money with the press of a key on a keyboard, but eventually that bubble bursts and takes the economy with it.
And all of this is subordinate to human nature, because that rules over everything we do. And basic human nature shows that people fare better and are happier and healthier when they are able to provide for themselves. People are also lazy and will mostly take the path of least resistance. Put those two issues together with a world in which people don't have to work, and you have a recipe for disaster.
If your desire for a UBI is driven by compassion, then it is misguided, because it would not be good for people who are healthy and able to support themselves. For people who are disabled, that's a different story, but that wouldn't be a UBI.
The point is that people would choose whether to work or not. Everyone would have that choice - live on a basic, low income, or top it up by working. If you've chosen to work then it's unlikely you'll resent those who choose not to.
Furthermore, even if that wasn't the case, think about the number of people who hate their jobs and resent going to work now. Getting that down to 50% of people hating their job would be an improvement.