[bodas]

$1 is a meal. You can't eat Whatsapp

[SmellyGeekBoy]

You can't eat a smartphone either but all of these theoretical people with zero disposable income seem to have them for some reason.

[EpicEng]

and if you can't afford $1 / year FB doesn't give two shits about you because you have no disposable income anyway.

[_emacsomancer_]

They probably do care, indirectly. They want as many people as possible on their service. Maybe you don't have $1/year for Whatsapp and therefore aren't of much interest to Facebook for advertising either, but your friends' friends might.