Do doctors and contractors have more sources of empirical data (or more widely known sources), or are they simply more willing to look for them?
I think the culture would be a vital part of an ecosystem of empirical observation. For the sciences generally, the culture predated the sources and gave rise to them. For medicine, I think a culture of empiricism was imported from other scientific fields. For contractors, they are very motivated to note what works, what breaks, and what enables them to make more money.