If you're going to disable the mouse and the arrow keys and really commit to the home row, more power to you. That is probably the best way to master Vim. But I think a significant number of people looking at Vim tutorials have never used the editor, and I think they deserve to know that there is an easy way to make the editor more comfortable and more familiar.

Someone down-thread used a metaphor to say 'the best way to learn a new language is by immersion' which is something I would agree with. But opening Vim for the first time feels like being dropped into a foreign country where no one speaks your language. Imagine how frustrated you would be to find that the people there actually do speak a language that you know, they're just refusing to understand you because you haven't issued the magic words, "set mouse=a"