People want to work and people need to work to feel like they have purpose in their lives.
UBI does not prevent people from working. Instead, it decouples the act of working from the means of basic support. The outcome is that people have more time to spend volunteering in their community, or taking care of sick parents, or pursuing an artistic endeavor that never would have paid the bills but that might benefit society. Of course people love to work — the premise of UBI is based squarely in that truth. If you give people an income, most people will not become lazy couch surfers like capitalists tend to think. Sure, maybe for a month or so, but then they start getting bored and begin to explore the world, to discover the purpose of their lives.