DeG: "can you tell me how come bad performers do not attend the Lewes Arms?"

Well, as I wrote on 19th Nov, I think this plays a large part:

It has a reputation, I believe, in the area for excellence - as does its sister club (brother?) the Royal Oak. I think any aspiring singer who wanted to perform there would be aware of that excellence - and would make the effort to give as much as they could. And they would be welcomed for it.

There's a huge amount of DIY music in various places in this part of Sussex, and there's no question (IMHO) that the clubs at the Lewes Arms and the Royal Oak have a reputation for excellence and dedication - which has an effect on would-be performers. Just my humble opinion...