It's not like we spend our entire time in the HW areas and I doubt that will be the case in SB either.
So much stuff is still in ARR areas, from beasttribes to PotD to events to FATEs and all kind of questlines - and you can't fly there.
I have 2 mounts on my hotbar, the Ixal wolf and one flying mount (usually Pegasus or a primal bird that goes with my outfit), and I can safely say that my beloved wolf is getting a lot more usage than the flying one