A couple of other people have touched on the main points.
In recent years, the MIP award has been going to guys who make significant statistical leaps. So, since Derozan already had decent offensive stats last year (17+ppg, with decent FG%), it's probably harder for him to impress the voters. Even if he finished the season with 20 ppg and 37+ 3fg%, he probably still wouldn't win, because some other dude will have made a bigger leap forward. An improved outside shot is not enough to win. Like Christtrip said, Derozan would probably need 22/6/3 to win.