"If a landlord, restaurant, cafe owner, asks performers to perform, normally he/she will have a FULL house and make a very nice profit from that evening. "

I agree with that and, of course, it would be unfair of him or her exploiting performers in such circumstances. However, was the festival in question and similar such events not organised independently of such such venues? i.e. by a festival committee or similar. Of course, if some of the organisers had vested interests, they could be open to criticisms but that wouldn't necessarily be the case. If it's music enthusiasts who wish to use a pub(s) or other venues and the owbners are letting them in free, that's surely a different matter?