If the developers could find a way to transfer 2D Sonic's physics manipulation over to a 3D environment, there wouldn't be a need for homing attacks. That's why I think they're mostly in place as substitutes for something better. On the other hand, many people like the direction Unleashed and Colors took with the 3D game mechanics; I'm not one of them, since I think the 2D Sonic games are more complex and replayable on the basis of their physics. I mean, people saw how gracefully Mario transitioned with 64, so the fact that the Sonic developers haven't accomplished something similar says something.