It's for economic reasons. Champions and high profile fighters can afford better equipment, train at more state of the art facilities, have better coaches, instructors, training partners, better nutrition and better doctors and strategy. Then there's the mental aspects, some fighters carry a lot of weight on their shoulders, whereas most champions and high profile fighters are more focused have far less stressors. Granted, if you train like most of these guys do, you're not going to go into a fight 100%. Training in and of itself involves breaking down the body so that it repairs itself stronger and better than before, when you train like these guys do, you will not be 100% come fight night, but you'll be a hell of a lot more prepared for a fight than if you were 100%.