Here is the thing...
Ask someone do they watch MMA?
Now ask if they watch UFC?
I bet you get two different answers.
My point (until I deleted it all) is that NFL / NBA / MLB have different promoting models. Right now the UFC just wants you to know about the UFC. The only way they can really do that is by pushing a few people at you and hope you get hooked on them and find fights you like.
Eventually, if they are super popular and every homes knows what MMA is, they can push more fighters and not just the brand.