Fox, Falcon, and Marth dashdance to move out of the way of hitboxes. They're able to do this because of the speed/distance of their dashdance.
Falco's dashdance is good, but for different reasons. The dashes are too small to reliably move out of the way of attacks, so it's not about that. Falco's dash dance is only good in combination with his lasers, not on its own. Basically, if your opponent knows when you are going to approach after a laser, he will be able to counter you every single time assuming he's good enough. Dash dancing after a laser hits is about making it look like you're about to run in, to make them act early, whether that action is a fair from Marth in an attempt to stuff a potential aerial, or a Fox dash dance avoiding a potential aerial. In the former situation, Marth is now in his fair lag and you're free to punish, and in the latter situation, Fox has now given up a bunch of stage for nothing. These are just examples, and it gets way more complicated with the amount of mixups present, but those are the basics of Falco dash dancing. It's to scare your opponent into doing something stupid while you're lasering, it is NOT for general evasion.