Why assume people will choose to do nothing if they don't have to work to survive as opposed to taking up hobbies, getting an education or doing jobs they actually want to do?
Some people will do healthy things and some people with do unhealthy things with their time. If those people are employed they're not able to sit around and do nothing.
There's downsides to working and to not working. IMO the downsides to not working for society as a whole should not be underestimated.