Emacs actually has a built-in tutorial. It takes an hour or two to go through, if I remember correctly. Most people don't do it, I think, because they think they know how to edit text - you just use the cursor keys and hit the keys you want to insert?
But if you follow the advice in the tutorial and practice over a day or two at a reduced speed, it does actually make a noticeable difference, IMHO.
It's a bit like touch typing. I know plenty of programmers who can't touch type. Yet, in my experience it actually frees a noticeable amount of brain power. But it does take maybe 10-20 hours to learn. So people don't do it.