Because there must be a coordinated effort to change the default or at least increase the diversity of layouts. Otherwise it's like teaching esperanto, putting them into a very small minority for little benefit.
Even as a technical user for decades I find it too burdensome to swim upstream with a niche layout, and I already have remapped copy-paste.
if swimming upstream is that hard (and i agree that decades of professional usage on a X layout is hard to give up); at least when teaching someone you could say something: “here is the layout you should use! i know mine is different and i can type typewriter with one row in case i want to impress someone but yours is better, like minor chances of getting a RSI and general efficiency when typing stuff…”
Maybe, but all that kind of assume you will only type on personal devices, or at least do 99.9% of your typing on personal devices.
When I worked in Europe for roughly 1 week of every month, I was largely flummoxed by the occassional need to use a foreign keyboard mapping (a German keyboard has y and z reversed from the English layout, as I recall). Just that and a few other differences for symbol keys meant that every time I had to use a keyboard not my own when in Germany, I went from being a fluent touch typist, to a hunt and peck typist. Same for French keyboards, which had several key re-arrangements relative to English that I no longer remember. If I taught my kids on Dvorak (which I considered, as they were home schooled), that would have been their experience on every device they encountered outside our home. I'm sure they would have loved me for it.
Even as a technical user for decades I find it too burdensome to swim upstream with a niche layout, and I already have remapped copy-paste.