The flip side of this is that doctors aren't infallible, and will often struggle with rare diseases that they don't deal with on a daily basis, or in some cases were never even taught about in medical school (such as recent discoveries).
It's true that doctors have to deal with a constant flurry of "I did my own research and think this bruise I got yesterday might be liver cancer", but sometimes people with legitimately debilitating illneses slip through the cracks and have to aggressively advocate for themselves to get any real testing done, particularly if they have a very "let's wait a few months and see what happens" type doctor who never seems to make any progress on their own.