Read more carefully. I merely said that people mostly do it as a challenge or as a cargo cult, doubtfully because it is a useful skill (unless you happen to spend an extremely large amount of time writing, which likely only applies to a small percentage of those that get told to learn Dvorak).
When I first got a computer, in college, my father recommended I learn Dvorak instead of Qwerty for ergonomic reasons.
My keyboard was one of the typical 80's/90's beige color, so I took a black sharpie and wrote the Dvorak equivalent on each key. When I was typing, I focused on trying to remember which finger had to move where for each character. If I couldn't remember it for more than a second or two, then I could look at the keyboard.
It only took a couple of weeks to get the basics down, and it was several weeks after that that a friend pointed out I had worn off the sharpie for my most frequently used keys (I hadn't even noticed) and I was typing at a speed comparable to all the Qwerty keyboarders in the dorm.
I really like Dvorak. I don't type much faster, but typing requires much less effort. If you know someone who types Dvorak, take a look at the wear patterns on their keyboard. It's pretty much the home row. Contrast that to qwerty, where the top row (especially the E key) gets an inordinate amount of wear.
It does take a minute or two to initially set it up. Here's an old listing of ways to do it on a wide range of operating systems - https://kb.iu.edu/d/aepk And I would recommend setting up a keyboard shortcut to switch between them.
Once you have it set-up, including a keyboard shortcut, switching your keyboard is just a shortcut away.
I only type in Dvorak, so I can't speak to the ease of a single typist switching back and forth. I have pair programmed quite a bit with Qwerty typists and other than occasionally switching keyboards and momentarily forgetting to switch it, it has never been a problem.