> Until setting up a private chatroom for your family is as easy as downloading an app on your phone

It already is - all my family and close friends are on our own Mattermost instance but it still has them have the same social apps everyone else has because two degrees out are not on our own Mattermost instance :)

This is absolutely ok! As the cost of providing a service becomes less subsidized and starts to reflect the true cost to service a user, more and more people are going to self-host. Hopefully federated networks take off then.