Good points, but what you need to remember is that PRS can only licence for copyright music. If the music is not copyright, then they cannot licence for it.
For example, if you have a folk club where all the music played is traditional, then you do not require the licence. But, as I'm sure you'll understand, if people start playing covers then the writers deserve the royalty.
I do think folk clubs in particular do get a raw deal, but it really is up to the members to bring this up with PRS, otherwise they won't know that people feel hard done by.