They didn't need those numbers for the iPhone to be worth their original R&D effort, but winning those numbers is even more advantageous for them because of their core philosophy around volume and margins.
Meanwhile, Microsoft/Google/etc are playing a whole different game. When they succeed, they also saturate a market, but that's the only time they call it a success and so they approach the whole product design process differently.
It's hard to call anything selling 200M+ units/year low volume.