The one major advantage is preserving sessions and re-attaching to them later, e.g. when you're ssh'ed into a remote machine or VM and you don't want to lose your setup.
Ratpoison could possibly be better (I keep meaning to give it a shot), although one thing I really enjoy about using tmux is being able to quickly open, shuffle, reorganize, and close panes with only the overhead of starting a new shell.
I happen to be a vim user. tmux, vim, vim-tmux-navigator, and some comfortable configurations in .vimrc and .tmux.conf can be a force multiplier for one's workflow. If you like vim, then it makes a lot of sense. If you don't, there's still probably some merit, but, maybe less of an incentive.
I've never used ratpoison, but just read into it. Sounds pretty great, actually. If the key bindings are simple enough, I suppose it could be pretty similar. But, as a sibling comment pointed out, it works most everywhere. Where I go, my configuration comes with me.
When you say scrolling, do you mean with something other than a keyboard?
I thought this is something I wanted, but when I finally got around to getting mouse inputs working the way I thought they should, I realized that mousing around a terminal is kind of weird. Granted, I still use my mouse for copy/pasta operations, but I hope to eventually break that habit in time.
Nowadays, it's basically a simple way to let process running after existing the shell and reattaching later, for me.
But I had much greater ambitions in the past which I've given up mostly due to scrolling, clearing scrollback inserting a bunch of whitespace instead of actually clearing, etc.
I scroll with the mouse a lot, it's more tolerable with the keyboard, but it's still not as good as native interaction.
It also messes with the colors sometimes. For some reason, screen doesn't.
Ratpoison could possibly be better (I keep meaning to give it a shot), although one thing I really enjoy about using tmux is being able to quickly open, shuffle, reorganize, and close panes with only the overhead of starting a new shell.