I do whenever I want two websites displayed next to each other or when I want to have them in separate workspaces, which is pretty often.

Yes actually. Ctrl+Alt+b opens a new browser window quickly and I go somewhere. I have it faster in muscle memory than switching to browser and ctrl+t and then opening whatever.

Same with terminal. My terminals (xfce4-terminal or kitty -1) both open so instantly that I can ctrl+alt+t and even while typing at high speeds, the next character is entered into the terminal.

I can type the below sequence of keys at high speed (realistic example that OCRs clipboard image):

  ctrl+alt+t vpng | ocr | ctxt alt+tab

without risking the startup time swallowing my `vp` keys

And yes, I disable animations for any kind of window switching mechanism including alt-tab/worksapce switch

At any rate, I believe ghostty has the same single instance mode equivalent.