Some people do a job for the pride of it because it must be done. I wouldn't want to be a plumber, but that doesn't mean there aren't plumbers who take pride in doing it. Same with the floor cleaner at the robot-tractor tyre factory.

Though I suspect on a long enough timeline, that job will be automated too and UBI will become a "here's a [weekly|monthly] stipend to live life on, but it's not too much to act truly foolish with."