I believe that capitalism works only because people need incetives that are aligned with society needs. Otherwise they will work really hard on stuff that uses resources but will not be part of sustainable system.
UBI probably won't pay enough to have high-speed internet in a two bedroom apartment in a popular city center eating at fancy restaurants three meals a day. It will be the absolute minimum to not die if you can't work. So, people will probably go to work to have a better life than that, but at least have something to fall back on if it doesn't work out. Having a fallback means startups, volunteering, self-care, all sorts of good things. The risk of starving to death living in a cardboard box goes to zero, which prevents a lot of people from doing a lot of things. It's a very real possibility in the current world.
I think people that read this site don't quite understand what "real life" is like in America. There are no paid sick days. If you don't report to your shift, you're fired. If you're lucky, you very carefully fill out the right paperwork and keep your job this time as a courtesy. (There is no federal protection here; for example, FMLA doesn't apply during your first year or so at a job. Some states do a little better, but with remote work, you'll find that most of the jobs are in states without protections! Happened to a friend, though their home state also offers no protections.) While you're sick, you still have to pay for rent and food. UBI is the acceptance that corporate America isn't going to cover routine events like receiving medical treatment. It won't enable people to party 24/7 for 80 years on the taxpayers' dime. It just means you don't starve to death if you get unlucky.
People will continue working to do a little better than merely existing, if they're able.
In fact Thomas Paine wrote:
"To understand what the state of society ought to be, it is necessary to have some idea of the natural and primitive state of man; such as it is at this day among the Indians of North America. There is not, in that state, any of those spectacles of human misery which poverty and want present to our eyes in all the towns and streets in Europe,"