It's about the level of interest in the fight from casual fans. A big headline fight where both guys are well known is easier for a sports book to handicap than two guys less well known. They wait until closer to fight time on replacement fights as well which is what Hendricks vs condit really is.
Andre the giant once had 117 beers in one sitting, then had wine with dinner.
You can argue if Andre would have been the best fighter ever, but you cant argue if he was the best drinker ever.