many different things. to cite a few

1. way too many regulations and lobbies that prevent any relaxation by scaremongering

2. unions that artifically constrain labor supply. doctors lobby to keep number of doctors low and regulatory capture preventing forign doctors from entering workforce. Uk for example imports doctors from india.

both political parties have their own agenda to not disrupt above . democrats love regulation and unions. republicans love corporate profits from regulatory capture.

healthcare is exterme opposite of freemarket despite the veneer