Because the dialogue we have doesn't actually pertain to the issues.
For example a common term bandied about is "Free health care." Nowhere is health care free. The idea of free health care is nonsense.
Perhaps people hear the term "free health care," and armed with that bit of misinformation -- and nothing else -- they conclude the notion doesn't make any sense, so they're against it.
Most Americans have not traveled to another country or learned to speak another language. And there is the notion of American exceptionalism. So when we find out our health care system might be made more like France or England, people are opposed. Even though they have no idea what health care is like elsewhere. (Or more likely, whatever ideas they have are wrong.)
There's a country song, the lyrics are "I've got shoes beneath my feet, and that's good enough for me." This is essentially why many Americans don't want health care reform. If America truly is, as Michael Medved is fond of repeating, "the greatest nation on G-d's green earth," then there is precious little we can do to improve on that. Don't mess with success. Nevermind that our system is horribly inefficient, it's American, it must be good, practically by definition. Heck, American muscle cars are inefficient, but who wouldn't love to drive a Camaro SS?
Another part missing from the health care debate is the concept of rights. The rest of the modern world views access to health care as a basic human right. Canadians, for example, feel that any Canadian should be able to be treated when they are sick, even if they are poor. Americans could embrace this notion if someone would present it to them. However, the competing idea, in which we have to earn our right to health care, is compelling and inseparable from one of America's core mythological beliefs, the Puritan Work Ethic.
Somehow people haven't noticed the idea we have to "earn" rights is exactly the opposite of what a right is. Many have said there is no right to health care, and even that extending such a right is unconstitutional. But the right is there, because no ER in any state can turn away someone seeking care, period. And noone has suggested changing those laws. We have an inkling of what our rights are but haven't seen them fully realized yet.
One cannot ignore the role of wealth. Most wealthy people do not want for health care. They are either covered by an employer's plan, can afford to purchase their own insurance, or simply pay as needed. Those without health care or with insufficient care are typically those who face more severe socioeconomic conditions. And it's seen as their "just deserts" for being lazy. (This isn't even touching on groups like the AMA, who care much more about doctor's pay than delivering health care to all Americans. Or the insurers themselves, who seek profit over all.)
Too many Americans subscribe to the notion "That guy is too lazy to get a job. Why should I pay for his health care?" It's the Puritan work ethic speaking. Perhaps it made sense a few centuries ago in Massachusetts, but that was before the advent of modern medicine. But it is pointedly obvious to anyone who has looked at health care around the world that it costs substantially less when health insurance is part of the national agenda.
Americans are either too stupid, too lazy, or (my guess) too wrapped up in their antiquated mythology to accept new, better ways of doing things.
Modern medicine is, practically by definition, "socialized." This is an inescapable truth. Epidemiology, the study of health and disease in populations, forms the basis for today's medical interventions. It is a study and a science which takes as its largest denomination the nation as a whole, or sometimes the entire world. Decoupling our health care delivery mechanism from our nation hampers our ability to achieve optimal outcomes.