I am personally from one of those third-world countries (India) and in my experience, it's easier to stop using Facebook here since the social fabric is already strong enough that you don't really need Facebook to be able to stay in connection with people. I quit Facebook half a decade years ago when I was 16 and haven't had to use it again.

People used to have social connections before Facebook came around and the methods to form and maintain those connections aren't dead yet since there is a large portion of population who never started using Facebook (my parents, for instance.