Earlier quoted context omitted.
This may be a little elitist, but if you're not going to use vim the way it's really made to be used, why even bother? I get that `mouse=a` makes it more familiar, but if you're always going to reach for your mouse, you're never going to really get used to the motions.
I think they were speaking from a total beginner's perspective, and how to get them up to speed as fast as possible. I felt the same way when first learning vim, since it was completely different from the code editors I'd used in the past, it was strange not being able to use the mouse in the way I was used to.
I find it much more useful to remove the ability to even do the wrong thing, than to simply try and will myself to do the right one.