Some work requires a lot of education -- programming, or surgery. The work itself perhaps is not so bad, and someone would volunteer to do it for free... but first they would have to spend years or decades just getting the necessary education and skills.

Sure, but a lot of work is just not fun at all, and practically no one is intrinsically motivated to do it. No one is going to become a plumber or garbageman for kicks; some kind of instrumental motivation is needed. I've noticed a lot of people on the political left are really hostile to the idea that some people have to do unpleasant work--and isn't just the fault of some arbitrarily cruel capitalist.

As I mentioned above, Corey Doctorow tried to solve this problem with "Whuffie," but I think Whuffie is fundamentally flawed, and would not provide a well-functioning incentive structure.