I think part of it is that what good is your TUI if it doesn't work with, you know, a terminal, hooked up on a serial port? Where you will be unable to have anything but "shifted" and "control" characters easily recognisable. Some terminals did have a "meta"-equivalent key that simply forced the highest bit on, making them INSTANTLY incompatible with anything but US ASCII.
Sure, you can write a TUI library that allows you to interact with "idealised terminal of choice", but I'd prefer one that works with one of the serial terminals I actually have, somewhere, around the place.
Sure, you can write a TUI library that allows you to interact with "idealised terminal of choice", but I'd prefer one that works with one of the serial terminals I actually have, somewhere, around the place.