I have an observation which may or may not be relevant or fair. When we were over in the US a couple of years ago, I got the impression of an imaginary line of competance above great, below it, nothing. We witnessed a very good Jazz trio in a Bistro and their "bucket" (the whole pay was by donation from the diners") was emptied frequently, my guess is they made a tidy sum for their evenings work, the following week they had a jazz pianist on, he wasn't in the same league, got absolutely nothing in his "bucket". There doesn't seem to be the same desire for self entertainment or for people trying the audience want the very very best or nothing. So, is that what is going on here? No, clubs/ sessions still have their characters and whole bunches of regulars of whatever competence and long shall it be that way, it is good to have guests as treats but the sustenance, the bread and butter, are the regular core who meet up to enjoy making music together, not sitting in silence listening to strangers.