I have no idea. Facebook, or all its faults, is more user friendly, and allows you to say more, and explain more, and show photos and graphs and the whole shebang, kind of like what we do here.
I think some people, do not enjoy, or simply cannot get through, long passages of discussions, so the super short, sound byte-esque way of communicating is easier for them to digest.
Can you imagine Trump here in Fluther??? I shudder to think about that. If that happened, I would love to see @Savoirfaire or @Zaku try to explain things to him. Or if our old friend @Gailcalled were still with us, she could tell him in no uncertain terms that “bigly” isn’t a word, and then explain our guidelines. And then the Mods could toss him out.