Conrad, you are quite the gadfly. It's hard to resist countering you..
I know of quite a few professional folk musicians who volunteer their time keeping their local folk organizations alive, and / or attend participatory musical events in their local area, sharing their music for free. I go to 2 festivals every year, entirely staffed by volunteers. Many of these "volunteers" are part time & some full time professional musicians. I have learned from many masters in these local, informal, free or low cost settings, & I am deeply appreciative, & I pass on what I've learned to even less experienced musicians. I am also fortunate enough to have the money to pay for concerts & lessons. I have no fear that traditional folk music will die out, because it got "too capitalistic".
Professional folk musicians often spend alot of time passing on their traditions & expertise for free, to their local communities, in informal settings. They don't need to travel accross country to perform for free, or give formal lessons or formal concerts in their local community for free, unless it's for a specific good cause, (far too many of which musicians are asked to support for free).
If a performer spends alot of time preparing for & / or traveling to perform or teach, they should be paid for that time.