Because, quite simply, it's a contract. And if the provider doesn't agree to make a contract with you, no healthcare is provided. As in this case of yet another doctor who puts up a warning notice to his patients:
“If you voted for Obamacare, be aware these doors will close before it goes into effect.” The note is signed Joseph M. Scherzer M.D. and includes the following addendum: “****Unless Congress or the Courts repeal the BILL.”
People who insist that healthcare is a right would enslave another human being to make him or her provide it. If they really mean it then they ought to take intellectually promising children away from their mothers and fathers at an early age and raise and educate them to this end, just as Plato discussed long ago.
Funny how it's the Democrat Party which is so enthusiastic for a new form of slavery. Didn't they have something to do with it the last time? That went well.