I love a GUI in many cases! But if I'm building something, I personally want it across Linux and MacOS at least (personal and work, respectively). TUI answers that problem quickly, easily, effectively, and efficiently.
I'm actually amazed that we have never gotten to a really good UI framework that is cross platform. I really just want something like SwiftUI that's truly cross platform, personally. There are a million arguments to say that we do have cross platform GUIs, but all of them lack in some major way.