If your boss walked in to your office tomorrow and said we cannot pay you anymore but you are certainly welcome to stay on as a volunteer and otherwise everything will be exactly the same, would you do it?
ummmm...no. I honestly can't think of a single 'job' that I'd want to do that for. And believe me, I enjoy my job. Sometimes I actually love it. But it, it takes my energy & I deserve to get paid for expending said energy.
The only think I'd do for free is some kind of philanthropical work where the good I was doing was my payment. But then I'd need to have some kind of income to be able to do that (maybe from FIRE?).
Too many people talk about "making your hobbies into a career", and that's just crazy to me...
I think it depends on your hobby. IMO, a number of hobbies, like photography, painting, & other arts can translate into some kind of money-maker, with minimal extra effort. And it could be worth getting the extra cash, if only so you can more quickly afford new toys to upgrade your hobby.
Other hobbies, like say...bird watching, might be a bit harder (although I guess you could become some kind of bird guide) & take much more outlay, especially in time.
I guess you could say that piano-playing was a hobby of mine for years. I played regularly from the time I was 4 until about 20. By the end, I was quite good, & did weddings, funerals, dinners sometimes. A lot of older, well-meaning people suggested I try to do it professionally, which I was pretty agast at. To me, piano is the kind of thing that, once you have to DO it every day, in a certain way, for certain people, it's no longer joyful & loses all appeal (not to mention all the competition involved in getting any kind of decent-paying job playing the piano).
Whereas something like say, photography, if you've got some really lovely pics that friends frequently compliment, putting them up on etsy.com & seeing if anyone buys them would be much easier, & doesn't seem like it would put a damper on the hobby at all.