I worked in a hospital system for a time—those documents are often integrated through a medical system where the hospital pays a recurring subscription, and the site developers just plug things through an API to display the documents from the central medical system.

Thus, you have one document that's identical across dozens or hundreds of different hospital and medical system websites.

A long time ago, I held more weight in results from reputable places like Mayo Clinic, but even their site seems to be the same as all the others now.