Primary-care shortage is growing especially acute in rural areas and in parts of some cities. The doctor is disappearing in America. And by most projections, it’s only going to get worse — the U.S. could lose as many as 1 million doctors by 2025, according to a Association of American Medical Colleges report. Primary-care physicians will account for as much as one-third of that shortage, meaning the doctor you likely interact with most often is also becoming much more difficult to see. Tasked with checkups and referring more complicated health problems to specialists, these doctors have the most consistent contact...