I personally like making (and using) TUIs because:
- They encourage developing simpler, information-dense, and keyboard-driven interfaces, which I tend to prefer in general.
- I find them more fun to write, and less aggravating to maintain and debug, than interfaces built with GUI toolkits.
- Most software I write for personal use is going to be run in both a Linux and Mac OS environment (and a lot of the time on a headless server to boot), and a TUI often has less fuss than other options (at least, IME).
- I think monospaced text in a terminal just looks cool.
I think the "fun as hell to write and use" angle is underrepresented in the comments—thanks for bringing it up.
It is, of course, completely subjective, but I know there are a fair number of people out there who agree with that statement.
But you can't really do information dense when you are limited to a fixed grid of monospaced character glyphs. Variable width fonts are much more information dense for example.