From the side of the Messanger, it could implement stories from pixelfed and communities from Lemmy/mastodon/kbin etc.
I don’t know if anyone is asking for this, but Whatsapp has both, so someone must be using them, right?
As from the side of every other fediverse app, I think it could be a good way of implementing DM functionality without developing and maintaining it for every single app. Maybe. I don’t know really, depends on how it’s developed/implemented