According to a recent Health Affairs article, the primary (but not only) reason is reimbursement rates:
Consistent with the results of prior research,8–11 physicians in the focus groups cited low Medicaid reimbursement rates as a serious problem that limited their willingness to care for Medicaid patients… Administrative data from 2010 show that the Medicaid-to-Medicare ratio for payments for primary care services was…61 percent nationally. [Doctors] estimated that the current Medicaid rates were covering roughly 50–70 percent of their costs of providing care for Medicaid patients.
Low reimbursement is not the only reason physician’s do not accept Medicaid patients; physician costs to treat Medicaid patients is also hire. To make treatment of Medicaid patients more attractive, Medicaid programs would need to: lower physician costs of participating in Medicaid (e.g., by simplifying administrative processes), speeding up reimbursement, and reducing the costs associated with caring for those patients. The last of these may be difficult to achieve but addressing the first two drawbacks is entirely feasible.
Of the physicians surveyed, 79.2 percent reported that they were accepting new patients at their main practice site, but only 50.3 percent reported that they were accepting new Medicaid patients. Overall, 68.7 percent of general pediatricians and 46.0 percent of the other primary care physicians reported that they were accepting new Medicaid patients. [Likely due to more generous reimbursement of pediatric services by Washington State Medicaid]
If Medicaid patients are able to find a doctor, however, their length of visit is the same as those who are commercially insured.
- Sharon K. Long. Physicians May Need More Than Higher Reimbursements To Expand Medicaid Participation: Findings From Washington State. Health Aff September 2013 vol. 32 no. 9 1560-1567.
- Brian K. Bruen, Leighton Ku, Xiaoxiao Lu and Peter Shin. No Evidence That Primary Care Physicians Offer Less Care To Medicaid, Community Health Center, Or Uninsured Patients. Health Aff September 2013 vol. 32 no. 9 1624-1630