It's not about lazyness. It is a matter of having all your needs and wants fulfilled and not needing to work. Where you can finally simply pursue hobbies. Why do any kind of labor if everything is met. Especially janitorial, plumbing, heavy lifting, dredging in miserable conditions, or any other number of difficult thankless jobs.
Go watch dirty jobs the tv show, it's an eye opener. There are even people who climb down in sewers and scrap our feces off the walls in big cities. Who would want to do that if they could just get on UBI and build gokarts in their spare time instead.
You know those wind turbines the power grid relies on? Dirty jobs had an episode that showed how they have to climb up inside them, crawl into really tight spaces, and clean out debris to keep the turbines functioning. It's a tough, harrowing, frightening and claustrophobic experience.