I'm thiiiiiiiis close to deleting Facebook. But I feel semi-obligated to have it for work and there are some people who I can only reach through Facebook Messenger. If I could somehow convince everyone I know to get Signal, it'd be much easier to leave.
Basically, as the article says (without ever using these words), it's the network effect on steroids. It's not just that everyone you know is on Facebook. It's that the whole world is on Facebook, and often *only* on Facebook.