The big difference is a pointer can be used on a touch UI without changing the UI. A finger can't be used on a pointer UI without changing the UI. Microsoft tried the changing UI and people seemed to not like that. If they don't change the UI, I could only see touch being used for gestures, not pointing.My view is it would be good as an option. Just as iPad is a touch first device, it offers a pointer experience.
It should be the same with a MacBook. It's pointer first but would be nice to sometimes touch what you see.