I think another factor is that people are rejecting the rounded corners and excessive padding of modern web design, you can't do that in a TUI, so you don't have a designer or standard practice encouraging you to do it. As implemented TUIs have greater information density than GUIs. Make no mistake though, TUIs are a decided step backwards from GUIs. Everything that you can express via text, you can also do in a text area on a GUI app.