I... personally have no idea. The main thing is with all these polls that @Bookhouse and numerous others do, the developers get to see from the players themselves whom they would like to see in the game. (Read: potential sales.) As well, if the developers are already working on one of the characters featured highly in one of these polls already (as in before the polls are created and voted upon), they would know there's a strong chance the character will be a raving success.