The reason lies in the game balance. The Arcade Edition includes characters who are deliberately unbalanced -- we're thinking Oni and Evil Ryu here -- in order to build "competitive spirit" among the people who hang out at arcades and play in short sessions. The home version of Super Street Fighter IV has been designed to better equalize the characters.
Of course, the absence of a standalone console release of the arcade version of the game doesn't preclude the release of Evil Ryu, Oni, Yun and Yang as Super Street Fighter IV DLC -- something Ono has proposed before.
Update: Ono has made several statements on Twitter suggesting that an Arcade Edition DLC announcement will be forthcoming after the release of Super Street Fighter IV 3D Edition. Thanks, Kreg.