Imagine you wrote up an ogre as a race, roughly balanced against the other races. Imagine, further, you wrote a few feats that would further advance your ogre-ness to the point you looked more like the MM ogre in capabilities. Would it be helpful to have a three level Ogre class to focus on ogre-ness?
What if the race in question was something that had more racial powers, like a dragon-like race or some kind of outsider? Would it be good to provide an option to delve more deeply into those powers, rather than spending general feats on them at a much slower rate? I've seen some of the problems of a Savage Species type approach, especially wrt to casters, but I can also imagine that it might be frustrating to have to wait quite a few levels to get all the goodies you probably picked the race for in the first place.
The other context, I suppose, would be something like: is there a place for a dwarf paragon class in Pathfinder? I haven't seen it done. Further, favored class bonuses, traits, and more modular classes remove a lot of the impetus for it.