I do not agree with you entirely. EM isn't supposed to be primary care, but unfortunately, because of the problems with our current health care system, it frequently does serve a similar (but not identical) role for some patients, particularly those without adequate health insurance, or those who are unable to secure appointments with their PCP. Most EM (not ER, by the way) physicians, by my observation, don't really like to play this role, but do it anyway because it has to be done.
I'm glad that these patients are getting seen for their primary care needs, in addition to their emergent ones, but it ultimately hurts both the system and the patient. First of all, it places an undue stress on EMS and potentially jams up the system for those who actually need emergent care. Secondly, the patients seen in the ED for their primary care needs aren't getting adequate follow-up and preventive care which is exactly what good primary care is supposed to be. The idea of primary care is that the PCP is the nexus for the patient's care. He follows the patient, keeps track of things through time, all of the patient's consults, and has a coherent, complete picture of the patient's health. This is not the same as an EM physician doing point of service care and then never seeing that patient again. That patient isn't getting adequate primary care; he is getting his immediate needs met, but nobody is tracking his progress and holds the entire picture.