Final answer:
Hospitals became centers for health care due to increased demand for services, consolidations during the hospital 'merger mania', advancements due to public and government-funded research, and the recognition of public health measures like immunizations as economic necessities.
Step-by-step explanation:
The factors that contributed to the emergence of hospitals as legitimate centers for health care include a shift towards a mass production and efficiency model in response to increased demand from America's aging and less healthy population. This demand led to the 1990s 'merger mania' where local hospitals and doctors' offices consolidated into larger systems. Additionally, the development of public goods such as sanitation systems, and the advancements in medical research funded by governments and universities, also played significant roles. Government involvement through incentivization of medical discoveries with patents and intellectual property rights further supported advancements in health care. Lastly, the importance of preventive measures such as immunizations became economically recognized for their role in mitigating illness spillovers, fostering a more robust public health paradigm.