Vim keybindings, one of the most powerful and widely supported ways of interacting with information, basically impose the "grid of text" nature that define TUIs anyway, so my message prompt has to look like a terminal. The rest of the UI can be whatever, but grid-of-text works well for structured output, especially code blocks, as well.
TUIs compose with tmux. Pi's homepage says "use tmux" twice on it. It fits right into an already-mature ecosystem including a clipboard (powered by Vim visual / line / block mode) and easy integration with shells, editors, and other tools. GUIs generally have to re-invent all those wheels (tabs, splits, sessions, etc.) and it never integrates as well with other tools in a totally cross-platform way.
TUIs compose with tmux. Pi's homepage says "use tmux" twice on it. It fits right into an already-mature ecosystem including a clipboard (powered by Vim visual / line / block mode) and easy integration with shells, editors, and other tools. GUIs generally have to re-invent all those wheels (tabs, splits, sessions, etc.) and it never integrates as well with other tools in a totally cross-platform way.