I don't see why clubs shouldn't be run as professional businesses. They should certainly be run in a professional manner. That is not inconsistent with operating as not-for-profit businesses, although if someone can run a club as a sustainable business, providing good entertainment, paying professional guests a proper fee, reinvesting in the business and making a profit as well, good luck to them.

Whilst people seem to be reluctant to fork out a few quid to see someone in a folk club, they do seem to be willing to pay considerably more to see a well-known performer in a concert setting. The larger capacity makes this financially viable, but you lose the intimacy of a folk club.