I relate with what you wrote a lot. The first question out of my mouth after learning something will be about why we are doing something in this way, or why not do it another way. I encounter this problem with my partner sometimes and I've spent a lot of time trying to understand it. I'll ask why we're doing some chore or errand and they'll get angry rather than provide a good explanation. Meanwhile, I am 100% sure if the roles were reversed I wouldn't ever feel a tinge of anger or get upset about it.

I believe it is a response that is ingrained in to people through trauma. Thinking back to school, I've had memories of people asking teachers "why" and the teacher going off on them and at best embarrassing them in front of the class. Even the circumstances where someone asks why, and a valid answer is given along with a dose of condescension, are memorable enough to me to consider it traumatic. If you have been at the receiving end of this treatment, you might learn the wrong lesson from it - that people who question authority or tradition are deserving of belittlement. If they have a good answer, you'll get a response with a layer of snark. If they don't have a good answer or aren't able to articulate it, they will get frustrated and only deliver the snark, rather than try and work through the articulation with you.

When I think back to these interactions with my partner, they tend to follow that pattern. I'll ask why, they have no good reason, but still give a sarcastic or hostile reply. I get annoyed at getting treated with condescension AND not getting my question answered and we end up arguing over nothing. (we've gotten a lot better about this)

I don't think this trauma is limited to when we're children, either. My partners boss has a toxic trait of getting upset when his processes are questions, and I am pretty sure my partner picks up on that and mirrors it when they come home (intentionally or unintentionally). Also consider hazing ceremonies, trainings, urgent decision making meetings. If you ask "why" are we doing this to a figure who is acting as an authority, it is implicitly viewed as a challenge to authority. I've been taught to never publicly question someones decisions and to ask the questions in private after the presentation/meeting, but would be delighted if someone questioned my process during a meeting, or better yet found a way to improve upon it.

Anyways, what's worked well for me and my partner, is explaining that I tend to ask a lot of questions and that they are in good faith. I wait half a minute or so for them to process what they just said in response to me, and follow up with something along the lines of "when I asked you why we're doing X, I was being serious. Maybe we're doing it because of Y?" and then they'll be in a better position mentally to correct me or admit that Y is the reason and Y is a shitty reason to do X.