The intention isn't to stop them learning how to Dash. The intention is to get em into the action faster, and let them learn to dash later when they want to get better.
Having a training wheel mechanic like this would get them into the game properly within a week, as opposed to 1 ~ 2 months. Once you come to terms with the main mechanics, turn off auto dash and spend 1 or 2 weeks learning how to dash. Meaning you'll still be fluent in the game within 3 months, but the quality of your overall game experience will be higher.
Just because everyones done it doesn't mean its a good way to continue dude. As a species we'd still be in the stone age with that logic.
That'd be another bit of the "Learn how to move properly or don't get it" bits. Dashing is 90% of the game for better or worse, and like I said, the biggest bar to entry to this game.
Take it from the guy who did this method to learn this game, Dashing wasn't hard to learn, but I got way more enjoyment out of this game by being able to toggle my dash at the start, then later spending about a week to dash right.