Another good article here:

http://www.vidwarren.com/should-the-artist-bring-the-audience/

We all know that
(a) this is a bad practice
(b) there's very little musicians can do about it except
(c) boycott such venues

But I do think that's why raising awareness of this issue is so important. It's an injustice, and injustices should be fought, not merely shrugged off with well-what-can-you-do. The powerless stay powerless otherwise.

That's what the Paul McCartney angle is undoubtedly all about: he does get the public's attention - all he has to do is speak out and a whole lot of people will hear him. If the message gets through to enough non-musicians, it could begin to bite exploitative promoters in the bum. It's one thing for musicians to avoid a venue, but there will always be others to fill in the blanks. However if audiences boycott places with this policy in sufficient numbers, it would grab some attention. They're not as replaceable as performers.

That could start to happen if all the promoter can get are second-rate artists who don't draw a crowd or keep them coming back for more. But in order to do this, the non-musos need to know about it.

The McCartney video is at least an attempt at achieving this.