"Because I said so" means "My authority as a parent should be sufficient reason for compliance. You asking for additional justification threatens my shifgrethor." Shifgrethor -- Ursula K. LeGuin's word meaning, roughly, authority simultaneously as the bedrock of the organization of society and as a measure of personal self-worth, is widely perceived as bullshit by neurodivergents, and it mostly probably is. But it is of prime importance to normies and if you challenge it, normies will inflict severe consequences. This is such a powerful lesson parents feel the need to instill it early on.
Except for the times when “because I said so” means “you are about to incur risk of permanent disability or death to yourself and/or someone else, and by the time we can have a reasoned discussion about it, it will be too late.” Cars, fire, heavy machinery, electricity are not “normies” and do not care whether anyone is neurotypical.
Why do people feel the need to point out this obvious straw man as if it's some gotcha? Can we not drag the conversation down to this level, please?
No one is saying you should calmly explain to your child that they should move because they are about to get hit by a car as a Ford Explorer bears down on them at 40MPH. Get the kid out of imminent danger, and then have the conversation, obviously.
If you usually explain to your kids why you're asking them to do things, then a lot of kids are going to recognize that when you yell at them to get out of the street with no immediate explanation, there's some urgency to the situation, because you've earned the trust that you ask them to do things for a good reason. But if everything you tell them to do has no explanation, then it's just another thing you're asking them to do for no apparent reason, so there's no reason to take the request any more seriously.
People are speaking faaaaar too broadly in this thread. "Normies", just like neurodivergent people, are a pretty wide group and don't all think alike--certainly they don't all put any importance on "shifgrethor".
And yeah, teaching your children how to interact with authority is obviously important. But notably, having any respect at all for authority isn't a requirement: I can obey an authority figure says even if it's stupid and terrible, if it benefits my goals. There are plenty of times in my career where I've done things I didn't agree with for bosses and clients I didn't respect, because other aspects of the job made it worth it, and they weren't worth risking my job over. Succinctly, "pick your battles".
Sure, as a parent, you need to teach your kids how to interact with authorities they don't respect, but being the authority they don't respect is a pretty terrible way to do that, and is going to have a lot of negative effects on your relationship with your child.