iOS actually does have a separate "internet access" permission for apps, but it's only available for devices sold in China.
So it's not the case that it'd be too much work or technically infeasible for such a permission to be available to us. It's just that Apple doesn't actually care about us or our privacy.
Probably impacts ads too much
It's funny you mention it; I've been cobbling together this link collection the past few days and your comment has spurred me to finally publish it: