Your anecdote, while I presume is true, doesn't address the main point. You should probably read
Gualdrapo's experience (https://news.ycombinator.com/item?id=32576061), and I find it true on large swaths of Latin America and Asia.
I, for one, would lose contact to a lot of my friends if I deleted facebook (and already have lost contact with some of them because they selfishly deleted their fb)