Access to primary care, a regular general practitioner or clinic a person can see without a long wait or a long drive, changes health outcomes less through any single visit and more through the accumulation of small, early interventions that never grow into something more serious in the first place.
Without that access, health problems tend to surface later and more dramatically, often in an emergency department rather than a scheduled appointment, which is both more distressing for the patient and more expensive for the system, treating a crisis that earlier, cheaper care might well have prevented from developing at all.
Communities with strong primary care access tend to show better outcomes across a wide range of measures, not because any single treatment is more advanced, but because problems are consistently caught and managed earlier, when the available options are still simple and the odds of a good outcome are still high.