True, but we're talking single digits if not less than 1% of the Android population there, regardless of the ability. And if you add Google services you're right back where you started.
Sure, but I'm talking about simply having the capability. If Google started getting ridiculous, regularly censoring apps, deleting data off people's phones, stuff like that, I can easily believe that there'd be a push to make installing an alternative ROM or OS a simple thing to do. Regardless, the option is there. I think there's a ton of value in that, even if the vast majority of users don't avail themselves of it.
With iOS, you live with what Apple lets you do, and that's that.