I think the corollary to this is that there are more people comfortable with living in a terminal. TUIs are more common now that there is an increased audience for them.
There's nowhere in a TUI to add oceans of padding for a ""sleek"" and ""modern"" look. There's very very little that a product manager can ""streamline"" in 80 columns of text.
As far my opinion goes, this is biggest (and really only) reason.