lack of governance over sanctioning bodies, they do as they will and that results in increasingly opportunistic organizations with billion belts and easy ways to dodge dangerous fights when two fighters who are not with the same promoter could meet
There are exceptions but largely they are there to please everyone so nobody is really forced to take the fights the public wants to see, we mostly only get to see them when it is too big to pass, if one of them doesn't seriously count with a fighter that's crossing over for a fight or if both fighters are with the same promotional outfit.
But there are too many times two or more fighters departed by their promotion and channels never fight each other or not in their prime cause there's too much on the line for both halves and they are not forced to make the fights either cause the abc organizations offer an easy way out.