If the history of the scene has shown us one thing it is the fact that ego's, conflict and self interest will always play it's part. There has always been rival promotions, with one promotion trying to undermime another or get the better of the other.
If the scene was left in the hands of one small group to "run" the scene there is a danger of complacency, at least with a variety of venues promotors are kept on their toes and have to deliver or they fall by the wayside. You will never get total agreement between promoters with different ideas of how a night should be and the policy. There is still plenty of sh*t going on behind the scenes with some saying one thing in public but behaving the opposite in reality.....too many egos and too many with self interest as you put it.
Also would a central venue catering for all work these days? The nighter crowd is slowly getting smaller and many have no wish to travel these days any great distance, many don't have to with nighter and soul night promotions all over the country.
Most promoters are making an attempt to co-exist in some sort of harmony, the nighter planner on here for instance but clashes are bound to happen with very few dates and venues putting pressure on promoters to put an event on every month, I've still 3 dates to find for Ginger and Andy's Dusk Till Dawn promotion as Sheridans want a nighter a month, a clash of some sort will be inevitable unfortunately.
Whilst I do think there are too many promotions the one thing we do have is choice, those that deliver the goods will prosper.