Because he is an active champion and wants the risky fights. There are too many champions that are so active before they win the belt, yet as soon as they get the title, their activity DROPS and they go "on holiday" and don't defend their belts until they absolutely need to. Pettis, Hendricks, Cain, Werdum, Aldo, Weidman, to name but a FEW. This can't just be "co-incidental". People hate on McGregor because he says a few "naughty words", but you need to appreciate him. He's an exciting fighter and turns up to fight everytime. He is not resting on his laurels after the first taste of success.