Not your parent, but here's my take. For remote usage, tmux doesn't provide much beyond vanity over screen, and is less likely to be installed on a shared host. Locally, I generally get by with &, bg, fg, and Ctrl-Z if I absolutely can't open another TTY, and a tiling window manager (or Emacs) provides a superior tiled workflow for the applications I use.

There are some cases where tmux could help me, but my X session and terminal emulators are stable enough where I'm not worried about them crashing and interrupting my shell session. As such, I have no need for tmux, and using it just for terminal emulator scrollback seems hamfisted.

The only use case I can think of is running large distribution updates which might potentially pull the rug out from under your graphical session, but I tend to run those on a non-X terminal if they look sketchy.

Edit: I'd totally consider using tmux as an alternative to X on my Raspberry Pi, but if I have X/Wayland, It doesn't offer me much.