Every text editor and most professional apps have elaborate hotkey schemes in practice, though. It's a matter of target audience and developer intent. There's nothing special about TUIs in regards to keyboard driveability, and they're heavily limited in just about every single way I can think of. Which is the main reason most TUI apps are simple and small utilities.

The very nature of being simple makes it so that the amount of hotkeys you have to learn is limited.

While most gui ones also have hotkeys, most people only remember a tiny selection and have to rely on navigating menus and dialogs to access stuff they can't remember which makes their usage very slow.

It depends on the goal, e.g. software like Maya is built for the world in which the amount of required work makes even average projects intractable if you're slow with your tools. Entire generations of actual masters of their craft have built their careers on being efficient with it.

Menus are also not slow by any measure, they're only needed for discoverability, can be navigated with the keyboard as well, and aren't that different from the menus many TUI apps have (e.g. Midnight Commander). Moreover, there are real novel ideas like Microsoft's ribbon, which basically combine vi-style input and discoverability. Hotkeys is just one way to drive a GUI app using the keyboard, out of many.