From the rally perspective, cars do have to be a certain minimum length for the World Rally Car class, 4 meters. Smaller is better, but Subaru no longer makes a hatchback or coupe, and Mitsibishi is sticking with the 4-door Lancer for now at least (As the street Lancer gets bigger and bigger, they are rumored to be contemplating a move to their Colt/Cyborg hatchback).
It's mostly marketing: Subaru didn't feel the need for a 2-door or hatch anymore, and Mitsubishi likes the Lancer. If you'll notice, the French teams (And Ford), who mostly sell cars to Europe where smaller cars are more common, are the ones using 2-doors. Obviously the Mitsubishis and Subarus work well enough, no matter how many doors they have.