People seem to think doctors exist in some special realm uninhabited by regular humans. That they are either the one expert that can never be wrong, or the one expert that is never right. They're just people, with a lot more education in a complex discipline but still people. Sometimes they listen and are good at their jobs and knowledgeable and thoughtful, and sometimes they don't listen, aren't good at their jobs and aren't as knowledgeable or thoughtful about their patients situation. I'm sure they're trained that patients should not self-diagnose because that's dangerous for them, and that attitude sometimes blooms in to thinking their patients are stupid and should be treated as such when they don't agree with their diagnosis.
It's like when my mom hired a contractor to repair the front steps of her house. She walked up one day and saw the guide wall they were starting was tipping away from the house. She mentioned it to them and was told essentially "butt out, we're doing our job." Low and behold, when the steps were finished, the whole thing started to separate from the foundation wall, leaving a huge gap where it was supposed to be flush.
Really it's that no doctor ever wants to admit they were wrong. Diagnosis is an art and a science, and for them, there are real consequences for being wrong. So they project this air of authority, rightly so, but that same authority often prevents them from ever re-evaluating something they said before, depending on the person.
Good doctors are willing to admit that health and diagnosis can be a fluid thing and adjust accordingly, taking it in stride. Bad doctors want to give you one diagnosis and stick to it so they can see their other patients.
I get this in tech sometimes. When something doesn't work, I'm the expert, my clients are not. My clients try to make guesses at what could be wrong. "Oh it's only wrong in this instance at this time, so it must be this." I often just straight up tell them "no, that's not how it works" because I have the knowledge and because software, unlike the human body, is something I can look directly at the guts of and that operates mostly on unalterable truths. Most of my customers go "oh, ok, you're the expert." Very rarely do one of my non-technical clients figure out what the actual problem is, that's why they pay me instead.