If I'm paying money to watch someone entertain me, then I expect a certain level of performance. However, I also acknowledge that this scenario is a recent invention (last 50 years or so) and has NOTHING to do with the folk tradition.

If, on the other hand, I participate in a singaround or ceilidh, then I expect all manner of abilities - good, bad and indifferent. Because that's the way it's been for the previous 900 odd years.