Look at john wayne parr, he fought 'caged muay thai', full thai rules with mma gloves in a cage. Leaving the opinions of people in the know to one side, from an uneducated fan's point of view, the cage itself is a factor that draws them to the event, and they want to see guys kicking the fuck out of each other (rightly or wrongly). This style of fighting is what the majority of casual fans expect to see from a 'cage fight.' Imo, mma should be the only style contested in a cage, but my opinion counts for shit.
Edit - side note
To be fair the jamaine facey fight was exciting.