Some people just don't care about this kind of stuff, even fairly intelligent people can be indifferent to privacy just because they're not terribly concerned about the worst that can happen.
I was watching a friend use their Facebook the other day and I was shocked at how noisy and sticky it is.
Personally, I'm highly suspicious of anything that is wildly popular. It's never long before that thing is covered in controversy.
So, yeah, out of principle I avoid IOS and Android and stay Debian/Open Source everywhere I can. It's not a perfect solution, but it's the best one I know of.