Primary care in the US is heavily reliant on the most basic heuristics to meet patient throughput requirements. Many clinics are operating at 15 min/patient. And no one wants to spend their free time charting the visit and making necessary orders (pharmacy, radiology, other providers, etc) if it can be avoided - so they try to cram it into that 15 min if possible. So they simply don't have time to ask the necessary questions and perform research.