To write software, I can use a CLI text editor, a basic GUI text editor, an advanced text editor like Sublime or Atom or VS Code, or a full on IDE like the JetBrains products. I have so much choice, and all of these are interoperable with each other and have different places where they shine. All work with git. I just don't think the same thing can be said for the document-creation workflows around law and such.
That's my general response to "why use 1970s tech?", though I guess I'm being a bit unfair here. Word is, in some ways, a marvelous piece of engineering. The whole Office suite is. Unfortunately, thanks to path dependence and business strategies, it's also locked in a place where it's not interoperable with anything outside the Office ecosystem by default.
I guess I have an answer to the age-old question: in sci-fi shows, how come nobody in-universe notices their computing technology is, in many areas, ridiculously inefficient and ineffective compared to the old XX/early-XXI-century tech? The answer may be, the sci-fi future tech is built on so many layers of lowest-common-denominator, walled garden, non-interoperable tech that people no longer know how interoperability or efficient computing looks like.
“Being old” is probably the lamest way to claim something shouldn’t be used.
Asking a world that is used to what came out of Xerox PARC to switch back to 1970's technology on teletype emulators is...the only word I can think of is Quixotic.