People get bored doing nothing, and enjoy contributing to their community.
No, they're not going to go get shitty factory jobs. But that's OK, because all those jobs are now automated and done by robots.
But they are going to go and do something useful, because that's what people do. The anti-UBI trope that "given basic income, everyone will just sit around on their arses watching TikTok videos" has been proven wrong in every study that measured it.