Outside of a pure development environment, you can't just install software on a machine. You have to create a change request and have it approved. And the latter just won't happen for stuff like tmux, there's simply no business justification for it.
I'm not sure if you're saying that myopic management won't see a business justification or that there truly is not one.
if you have to login, you wont be installing it everywhere.
and yes, we automate it. if I am logging in, it is for post mortems.