I like RDA a lot but I think there are a few reasons as to why he doesn't appeal to the masses or the casual fans. One would be that he isn't a prolific finishes, 12 of his 25 wins are by decision. Another would be that he doesn't talk shit, he kinda gives the standard cliche answers that we've heard a million times.
Again, I'm a fan but this is why I think he isn't more popular.