Many people (myself included) don't _want_ the newer marketplace / open community aspects of Facebook to be mixed into a platform where they share personal updates. If that means I have to give up 100 likes and comments on every baby/puppy picture I post, that seems like an acceptable trade-off to me. If folks want to comment on any of my updates, they can communicate with me in other channels (e-mail, text, real-life). Not for everyone, but it's definitely a market niche that's under-served right now.
A bike is a perfectly valid replacement for a car for the set of people who only drive a couple of miles to commute to work. It's obviously not a replacement for all users, but that doesn't undermine the valid claim that it is for some.
If it supported ActivityPub and perhaps WebMention, this would be possible, and across any social network.