I hear alot of whining about there not being “A” Heavyweight Champion, so why do people not complain about…

There are a couple reasons why its different in my opinion. (1) In boxing you do occasionally see the champions fight each other to unify the title and this happens because of (2) In boxing regardless of the association the rules are basically the same. In MMA just with some of the examples you mentioned their are rules and regulations that are very different. For example in the UFC they fight in a octagon shaped cage while associations like Pride and K-1 fight in a standard ring and thus the strategies are different. There are some big differences with some of the organizations in MMA ie K-1 is standup fighting only while in the others such as Pride and UFC you can take the fighter to the ground.

The biggest difference though is money. In boxing any title fight is gonna make big bucks and having two champions fight is gonna make both associations so much money that they dont really care if their guy loses. However in MMA a really good example is a fight alot of people were wanting to see UFC’s Chuck Liddell vs Pride’s Wanderlai Silva as both fighters were considered hands down the best each organization had to offer at the weight class. However both sides wanted the fight to happen under their rules and then both sides bawked cause neither wanted to risk having their champion shown up and MMA fans thinking that the other organization has superior fighters.