I don't use Twitter and don't have any friends that do. Am I just uncool, or is it super niche now?
Most of my non-tech friends in real life broadly do not have Twitter accounts, or if they do, they follow about eight people (usually including Stephen Fry) and have either never tweeted, or only tweeted about four times, usually starting with, "Well, I'm on Twitter now. What do I do next?"
I'm talking about people in their 20s and 30s here. The same set of people do make a lot of use of Facebook (though a few, like me, find it vastly irritating and have deleted their accounts in recent years - but I'm not sure I know anyone female in that age bracket who doesn't have and use a Facebook account).
A bit more anecdata while I'm at it: Instagram seems pretty popular in cities, where people enjoy posting pictures of their pulled pork burgers and cocktails in jam jars - out here in the countryside, I don't hear much about it. The younger generation definitely do use Snapchat and the like, but I think most people over about 25 have no understanding at all of it. WhatsApp seems to have a very broad and universal appeal, and is a real common denominator for anyone who falls under the category of "I want to keep in contact with a friend who lives abroad" (I don't fully understand how it won out over Skype, apart from Skype being a very poor experience on mobile). Lastly, I'm not sure I know anyone who doesn't work in online media who actually uses Pinterest.