This is because Medicaid so severely underpays doctors, as a clumsy attempt at cost control, that doctors lose money seeing these patients.
FORBES: Anecdotes vs. Economics in Health Care Policy
2.
The states could then provide federal assistance to the poor to purchase the private health insurance of their choice, freeing them from the Medicaid ghetto that so badly underpays doctors and hospitals that the poor on Medicaid suffer trouble in finding essential care.