[electroly]

There isn't much obvious benefit in using TUIs, but writing TUIs has a big upside: it's easier in most ways. It's trivially cross-platform, you don't have to make pixel-perfect GUIs (because it's impossible), you don't need icons or graphics (because you can't show graphics), etc.

[ofseed]

That's the main reason. TUI programs can be created quickly, and they're mostly developer-oriented, so they just need to be useful enough and don't need to be optimized as much as a GUI program.