My bet would be both. After all, why handle all the dirty work of implementing real-time chat that works across multiple different sites when you can just plug in Keybase instead? After all, if you're using it for encryption you already require people to have a Keybase account to have their chats encrypted.

Why would you install different Mastodon servers when you can go to twitter.com instead?

I don't :P It's too tedious to keep an eye on multiple communities and manage my single identity.