Right, not having to leave the terminal is a big one for me too. I live there and every time I start some desktop app, I gotta switch gears, potentially grab the mouse, leave my vim keybinds behind and leave my font and color scheme behind. I just feel more productive on the terminal then on desktop apps.
I think also a big problem of desktop apps is that you have to deal with window management. Now that I am on Niri it is really apparent to me how much I hated juggling windows in pretty much any other window manager that I ever used, except, interestingly enough, tmux.