It comes down to the old saying for doctors, "when you hear hoofbeats, think horses, not zebras." Rare and dangerous things often manifest in ways that look really similar to relatively harmless and common things. Go forward with the most probable explanation and you're not only going to be right the overwhelming majority of the time, but also keep costs and stresses down for patients. Only when somebody does show up with a genuinely serious condition (or otherwise had significant red flags) do you jump to zebras.

This is likely even more true in modern times with such high rates of anxiety and other similar disorders paired alongside the internet - there's going to be a lot of hypochondriacs suddenly thinking, and subsequently claiming, that they have every symptom of [something awful].

Doctors have very little in the way of legal protections, but malpractice has to actually be malpractice. A recent study on the topic found that in low risk occupations, 75% of doctors end up getting sued for malpractice over their career, and in high risk it bumps up to 99%. [1] When people don't like the outcome, they sue, but in most cases the outcome was largely unpreventable even with a high standard of care.

[1] - https://www.reuters.com/article/us-doctors-idUSTRE77G5YS2011...

If zebras cause blindness, perhaps you should consider zebras?