I think you've made an interesting point there.
If we're honest, which events, especially in terms of soul nights, are the best attended? Generally the ones playing familiar oldies.
IMO this will not be the case for too much longer as the "nostalgia" crowd gradually go out less and less, but currently..... anybody who tries to put on a night which varies from the safe formula is taking a risk.
I, and probably a good few others, have DJ'd at more "specialist type do's" for petrol money... because we want to see a particular event do well, i.e. its an event with a music policy that appeals. I wouldn't do that though if it was yet another oldies night put on in an already saturated market.
Going back to another point, however, those that hump the leg of a progressive scene but then only attend events which they promote/ DJ at.... have got all that's coming to them, IMO.