My opinion is that TUI is just a GUI with less fidelity. Being composed of text characters provides no additional benefit other than a retro style. The benefits of the terminal are outside of TUIs - composing scripts, piping data, bash etc.
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.
I do a fair amount of CAD so I'll use that example. Nobody who uses CAD professionally is clicking all the little buttons for tools. They're using commands, shortcuts, scripts, etc.
A GUI is slow and clunky. A textual interface, once learned, has way more degrees of freedom.
My two cents is that having all of your text be monospaced is not really ideal for agentic workflows where you do in fact read a lot of prose and in the future may want diagrams, rendered from a full browser's capabilities, etc.
I think I like the aesthetic of using a TUI because it makes me feel more like whatever 'real programmer' means to me... but I recognize its also cope.
(Also TUIs made a lot more sense when code was more expensive, because the monospacing constraint made it faster to build UI, etc.)
Yes, power users often use shortcuts and automation, but how is that an argument against GUIs?
It simply depends a lot on the actual task. Certain things absolutely require a (high fidelity) graphical interface. Other things can be done just as well (and with less distraction) in a simple TUI. You can't generalize.