The roof cam is basically the same as the "third-person"-cam, except you only see half of the car, so there really isn't a point to it.
I'll tell you why you're incorrect. As a number of people point out, cockpit view is unsatisfactory to many of us, so we use the other three. But bumper cam doesn't give you a good sense of how well the car is taking turns without a lot of practice, and you have no peripheral vision to the sides.
Chase cam gives you a great view, usually, but then you're looking from where the car was a fraction of a second ago, and the sway in the cam can make the car feel sluggish, plus turns are more difficult because you can't see the road from the point of view of the car.
Roof cam gives you what the other views lack.
- A view of the sides, rather like you have with your real life peripheral vision.
- You're looking down the track from the center line of the car, making for a better feel of the car.
- You're positioned over the center of gravity of the car, or at least the center line of it, giving you a good feel and view for taking turns.
The argument for cockpit view is reasonable, but for most of us, the view of the road is atrocious, very letterboxed, not like real life at all, making it seem like you're driving from the back seat.
As I and others have said, giving us these four views, bumper/hood, cockpit, roof and chase, AND making them configurable, is the best idea and will make everyone happy.