This is a confusing concession. Of course we love TUIs because of the UX, what other reason is there?
Constraint breeds consistency and consistency breeds coherence.
Take 1,000 random TUI designers and 1,000 random GUI designers and plot the variations between them (use any method you like)—the TUI designers will be more tightly clustered together because the TUI interface constrains what's reasonable.
Yes of course you CAN recreate TUI-like UX in a GUI, that's not the issue. People don't. In a TUI they must. I like that UX and like that if I seek out a TUI for whatever thing I want to do, I'm highly likely to find a UX that I enjoy. Whereas with GUIs it's a crapshoot. That's it.
It constrains what’s possible, not what’s reasonable. For example, one could typically fit more text on a screen by compressing it, but most of the time, that’s not the reasonable thing to do.
I’m saying most of the time because of the existence of English Braille (https://en.wikipedia.org/wiki/English_Braille#System) which uses a compression scheme to compress frequently used words and character sequences such as ‘and’ and ‘ing’ shows that, if there is enough pressure to keep texts short, humans are willing to learn fairly idiosyncratic text compression schemes.
colorforth (https://en.wikipedia.org/wiki/ColorForth) is another, way less popular example. It uses color to shorten program source code.
One could also argue Unix, which uses a widely inconsistent ad-hoc compression scheme, writing “move” as “mv”, “copy” as “cp” or “cpy” (as in “strcpy”), etc. also shows that, but I think that would be a weaker argument.
A "proper GUI" is rarely better than a well-designed TUI for communicating textual information, IMO. And the TUI constraints keep the failure-states for badly-designed UI tightly bound, unlike GUI constraints.
When you are "drawing text everywhere", you end up not having to draw all that much text. 3d models have more and more polygons as graphics cards improve, but the 80x24 standard persists for terminals (and UX is better for it). And I'm not even that convinced of "relatively expensive". Grokking UTF-8 and finding grapheme cluster boundaries has a lot of business logic, but it isn't really that hard. And unless you're dealing with Indic or Arabic scripts that defy a reasonable monospace presentation, you can just cache the composed glyphs.
(I'm not actually sure what the UX of TUIs is I love so much. Relative simplicity / focus on core features? Uff, notepad wins this one on vim. Fast startup times? I use gomuks, that takes a minute for the initial sync. No mouse? Moving around in TUI text editors with hjkl is slow. I either jump where I want to go with search or use the mouse. Lightness over SSH/network is the only thing I can't come up with a counterexample for.)