It's an accepted fact that Medicaid does not pay the full cost of billed care (often cited as 80%). If you expand Medicaid coverage who ends up paying the difference?
Answer: The people who are still left. The more Medicaid grows, the higher the medical bills become for the people who remain left out -- which happens to be the self-employed and the working poor.
By stifling self employment and cheating low wage workers in this way you force people to choose between poverty and wage-earning for large companies. The economy you wind up with gets slowly eviscerated as the two most important routes to independence and prosperity are shut off from anyone who does not have already have a lot of money.