TUIs are a really great way to mix GUIs into CLI "suites." For example, one may usually use homebrew through a CLI, but one can imagine that certain workflows with homebrew might be better served through a TUI than a CLI. Perhaps browsing and filtering the list of packages -- though the specific workflow isn't important for this example. In that case, homebrew can ship a CLI that handes most or all workflows, plus one or more TUI workflows to enhance some subset of those workflows. Because you're already interacting with it in a terminal, it's a pretty smooth transition to give you the rich TUI experience when appropriate. The same could not be said of a native application.