I believe ease of use is the #1 reason people stick to non-federated networks, even the governments.
Email, I send a message directly to a person or a group. This makes the idea of a federated network a little easier to wrap your mind around. I sign up for a Google or Yahoo email service. If I’m a big nerd I set up my own and send/receive email with anyone.
Social networks, I send a message to whoever wants to listen. This is easier to understand on a non-federated network. It also doesn’t help we don’t have a Google or Yahoo microblog service. There is Mastodon and which Mastodon server do you want? This is why I’m not fundamentally opposed to Threads. I share the general concerns of it taking over and not cooperating with the spirit of federated networks, but if all there is is Mastodon people will continue to be confused.