Of course you're allowed your opinion, as are we all, though saying "These pick n mix nights are just to get people in who don't like soul .. to fill the room up" comes across more like a statement of established fact rather than opinion, and I know it to be wrong in some cases.
The promoters taste has a great deal to do with it, as music policy is often a reflection of their taste. If it was just about "getting people in" there would, god forbid, be even more oldies nights dealing in the safe and familiar. If the music policy of these promoters does not coincide with the taste of sufficient customers obviously the night soon falls by the wayside, but there are mixed events that stand their ground, as Spacehopper pointed out.
Another point is that it's not exactly a new concept to have more than one genre: Look at a few old playlists from The Wheel.
You included on your list Betty Lou and Bobby Adams and it's stretching things a bit to say that's soul rather than R&B, IMHO.