it's more like "I am a tiny replaceable cog in a huge money-printing machine. if somebody is going to collect the paycheck anyway, why shouldn't it be me?"
making the hard choice is easy when you have nothing to lose, and it's even easier when you're so rich that the losses don't matter. the folks in the middle have just enough that it would really hurt to lose it. I can't say I blame them for guarding that jealously.
phone # + code is already the most popular method outside of the US, and gaining a lot more traction within the US. Login w/ Facebook does not really affect the success/failure of an app unless you really need their data for your app to work.
"My cog in the machine is not hurting anyone, why should I care" is how things get very, very bad.