It's ridiculous and one of the reasons why MMA is so popular. You have multiple world champions yet the two best at their weight won't fight each other. It's like Manchester City saying they're joining the Scottish league because they don't want to lose to Arsenal. The trouble is that both fighters will say the other is at fault but if you strip the belts from them they'll still be the best, they'll still not fight and you'll have another four world champions to make the situation even after.