I think that's what I mean though - its hard to sit and concentrate through a varied set of performances, some of which will be too similar to eachother or not really of any great quality. Its a little harsh to say that if people talk when you're singing then you're not good enough - they might be chatting because they lost interest two performers ago. Another factor is that some people will always do the same song, or sing in exactly the same style, each week - and then it gets very hard to listen attentively because it becomes boring no matter how good the execution (ok there's probably some exception that proves that rule).
In general a pub session is not the same quality as a properly planned and executed concert, and neither does it need to be. A pub session is a social occasion as well as a musical event - and if that's not the intention then what is it doing in a pub?

Kris