They disregard certain symptoms because they went to med school, had a residency and are a practicing doctor for 10 years. They see so many hypochondriacs, that if they did that, they could only see half the people, or even less.
The rule of medicine is "if you hear hooves, think horsey, not zebra". People googling their symptoms won't find their disease 99.999% of the time. You won't beat their experience by googling, that's not how it works.