Don't mean to be funny but a clue in the name - Auto Cycle Union which means every member has a say in what goes on. Every club member has a say, every club has a say, every centre has a say so not sure who needs to stand down - all of us.
I think what you are saying is why don't the young, new, enthusistic ACU members please stand up.
The ACU officials you are talking about are formed from volunters giving up their time and money to put on and run trials.
Probably the MX guys you refer to are profesional promoters in it to make a living. Triple the entry fees and we could all do something different but might not have so many riders