Plain-text files are actually not widely used outside of software engineering and when they are, they are used like binary and only edited with graphical editors. And most non-tech people don't see the benefit if it is there - in software development versioning was born from pain: big source trees are unmanageable withoud SCM. For typical office documents you miss some benefits but can live without.

One interesting anecdote / micro case-study: In my family we have a vacation home that we rent out. My mom (>70 years old, completely non-technical) manages the renting and updates an online calender where guests can see which dates are available at what price. I developed a very simple custom text format and a static site generator an my mom changes the data using the web-ui of my gitlab instance. I had to teach her but now she is very happy with it and much faster than with the previous solutions. And git helps greatly because mistakes do happen and its very easy to revert and see when they happened etc..