To give your life a purpose? To do something meaningful and fulfilling? To build something cool? To be able to afford additional, cooler things? To work on a common mission with likeminded people? To contribute something back to the system? To experience how things work in the background? To have a sense of ownership over your productive output?
And if you wanna express yourself creatively or just do nothing for a while, that's fine by me too! I'm sure you'd get bored after a while and want to make yourself useful again, so I don't think you should starve in the meantime.
That's our point. The limit of this is no serious social collaboration. You can't have cities, you can't have industry, everyone lives in small tribal villages until they get run over by other industrious people.
Oh yeah I forgot that's why I deal with insane corporate administrative bullshit to write bad software that solves problems only generated because of the scale of the internal social interactions: because it gives my life meaning.
You have hobbies and personal relationships to give your life meaning, you pay to be allowed to do that not the other way around.
Then why wouldn't I just stop working? Why bother working at all if I'm guaranteed to be subsidized by other people?