We're not talking about every single answer.
We're talking about when people say, in a meeting, "Well, can you justify that?" or "Why do we have to do that?" where the simple answer isn't enough and you're explicitly asked for more. And then I provide simple and complex answers simultaneously, but often at a later date (because opposite me is a pseudo-expert I respect who disagrees and his boss who knows nothing and won't understand the full thing).
At that point of asking, "normal" (non-autistic-trait) people switch off and rarely care as they've formed their opinion already, it's in opposition to yours (or they wouldn't question your reasoning), and they're asking for justification enough to change their mind. And then they don't look at it, or they do the "Oh, well, that's beyond me, I didn't read it all"... and then go on to make the decision the same way anyway because - presumably - it would make them feel foolish to be seen as taking advice, and they'd rather actually be PROVEN wrong further down the line when it's too late to backtrack.
Agreed that, by default, I provide the reasoning and answer, because it's just that often that the answer isn't enough or leads to a demand for the reasoning anyway. By the time it's got to an email chain, Yes or No won't be good enough.
But people believe that the "minutes" from a meeting are all that matters, not why those decisions were made or who made them, which is why I get things explicitly minuted in some meetings so I can go back later and, effectively, do an "I told you so". Without that explicit demand, it gets claimed that all the reasoning behind the decision was unimportant even when that reasoning is shown correct (i.e. we shouldn't have done X because Y would happen, we do X and - shock - Y happens).
And it's not even as simple as just avoiding blame / liability, or covering up, or failing to admit a weakness.
As you point out - if you trust the expert opinion you're asking for, you don't need the full explanation. I certainly have done this to those below me - "You're sure? You know how to do that? And it will solve the problem? Cool, I'll leave it with you.".
And I will happily provide Yes/No but that *is* opinion, because when it differs from theirs I'm ALWAYS asked for an explanation. In fact, being asked for my reasoning is the prime hint that I'm about to be overruled anyway.
There are many times where my boss has needed to spend upwards of Â£100k on my opinion. A Yes/No has sufficed, because they don't understand but they can see that it's a no-brainer to myself, even if it's hard to justify to a layman. It does happen. But when opinions differ and reasoning is required, it's ignored or needs to be so dumbed down as to be unconvincing and useless.
The second you involve other departments, staff, layers of management, etc. everything turns from Yes/No into "justify that", and then the justification ignored for a pre-made decision, and even swept under the carpet so it can't come back to bite them later. Often, you don't even find out their reasoning for overruling, which is the EXACT thing they asked you for. Even "Oh, we can't afford that much!" - that's a valid reason. When you're not prepared to give that it makes me question motives.
I've worked in several places where THE MOST ILLOGICAL decisions are made almost every day. There's literally no rhyme or reason and all those carrying out those decisions cannot see the logic behind it, even if they assume bad-actors, monetary gain, power-grabbing or whatever else as the reasoning.
As the person I am, I combat association with those types of decision by providing - on request - my reasoning. To use your code-analogy, I am "open-source". Not only do I tell you what I'm doing, I tell you why, and what else has been tried, and why that failed or isn't suitable, and why we should do things exactly THIS way.
And then, effectively, someone else buys their brother-in-law's piece of junky proprietary software and we're stuck with it and then I get blame from all corners for how we allowed it which, without stating reasoning as to why it's a bad idea in the first place, would be untraceable to anything but me not providing that reasoning and "going along with it" (really, being overruled and told to do it)..
I've had it happen for everything from Â£50k print contracts, to core business software. After years of dealing with people trying to push blame, or kowtow to bad decisions, and not having the social tools to combat it at the heart (which seems to involve doing it, wasting money, and hoping that you'll become mates with higher people by doing so), I provide reasoning.