Scarcity of resources is the ultimate driving force in any health care system. There are limited resources to provide for what is ultimately unlimited "need". I say unlimited because there is almost no limit to the amount of health care that could be beneficial to provide to our citizens. As medical advances continue there is an increasing number of possibilities for health care interventions, and these are certainly not getting any cheaper. We can not afford to give every possible treatment to every person. Under a SHC system the government must determine which treatments they will pay for and which are too costly. There are essentially two ways to match the resources with the demand: provide care for more people but provide less care, or provide care for fewer people so that those fewer people can be given more extensive care. I believe that human nature will ultimately lead us to favor the latter. When the decision makers are part of this socialized health care system, they will want to ensure that they get all of the coverage possible. In order for that to happen, however, many will have to be excluded.
The question then becomes who will become excluded. We have already started the process. Children that would require additional medical care, educational assistance, or any other "burdensome" interventions are already being targeted before they are born. (Incidentally, or maybe not, the founder of Planned Parenthood and the founder of the largest private provider of abortions in England were, to varying degrees, advocates of eugenics) From a fiscal standpoint this makes sense. By eliminating that cost we are able to provide more care for the rest of us. Euthanasia continues to become more acceptable and is even encouraged for those who would require extensive and expensive medical intervention to stay alive. Our current system allows the "healthy" and "productive" members of society to determine the rights of the feeble and voiceless. Socialized health care will further protect the strong at the expense of the weak.