The thing is... tmux etc etc are very much "hobbyist" tools in comparison to what Red Hat deal with. Red Hat doesn't want you to have to have a persistent shell session on a server - they have all manner of tools for central management of servers that you "should" be using instead, and needing to SSH into a server should be a very occasional thing.

Look at it this way - the primary use for tmux is having one's SSH client running all the time. Personal servers vs corporate ones. Barely anyone working on system software for Linux has anything to gain by supporting personal servers.