Only really in-deep players pick chars like ZATO (sama~), Millia and Venom.
Why? Because they're too damned tricky a lot of people would get discouraged of trying them. Not everyone will be willing to master Zato's Eddie attacks, Millia's precise combos or Venom's zoning.
Heck, I remember a friend who thought he was mastering Millia, but only thing he ever did was to mash that hair attack (forgot name) and he quickly dropped the game because:
1.- He never improved.
2.- He got scared after seeing one of those retarded Robo Ky's combos involving HS FRC.