The government can and should provide funding to research and develop new technologies. I've got good health insurance now. Because there is no guarantee you will keep your insurance if the premiums increase, if you lose your job or if you retire. There is also no guarantee that your insurance company won't reduce your benefits to reduce costs. Finally in the current system you pay for others' lack of insurance through increased premiums.
Someone has to pay hospitals and doctors for the care they deliver.
Thus the cost of treating indigent patients gets passed on to you. If you let the wealthy skip to the front of the line by paying an extra fee, you will destroy the pressure to keep funding adequate for the system as a whole. This is apparent in the British system and in our Medicaid system. A good example of how having everyone in the same system works to the advantage of keeping quality up is that in Canada several years ago, Mrs. Eaton of the Eaton chain of department stores had to wait a few days for her CT scan. That was a major stimulus to the system as a whole getting more CT scanners.