That's a good question and I think it depends on the developer. One recent day I became fed up managing my three separate terminal windows with each having a few tabs. I thought "alright, now's a great time to jump into a multiplexer" and it worked well as a catalyst. I downloaded Tmux, set a Tmux shortcut browser window for easy reference, and mimicked my setup in Tmux.

It's immensely a cleaner solution than toying around with separate windows for me. Switching sessions and consoles is seamless and it's all in one window. Eventually something will bite me regarding Tmux getting in the way of something and causing headaches but the momentum I have is great.

I suggest trying one out sometime, it may open a whole new world of tooling for you! Otherwise there's no sweat if you got something working sans multiplexer.