Because there's just nowhere in the overworld that really needs it. If there's any sort of ledge or gap, I'm gonna be gliding, or hitting the wall and climbing over it.
Like Goro pointed out, shield surfing is the only other real use for it, so I probably wouldn't really miss it if it were gone.
I mean, the only time I really need to jump is when I'm climbing up a cliff. It's not ever necessary otherwise. And as long as you're careful, you don't really need it in any classic Zeldas either.
That being said, never forget that my first time playing Zelda was helping my brother with WW on...