Speaking from jaded & bitter experience here, it's probably because the people who pay in are rarely the ones who benefit. It pains me to admit, but I've met more than my share of fellow Americans with an entitlement complex.
It's always funny when you get some guy saying no healthcare is better than publicly funded healthcare. 0k, the NHS has its problems but those problems are ones that all hospitals have, i.e. management bloat. My experience with the NHS is speedy service that is available to all regardless of income. I personally know at least two people who would be DEAD if not for free health care in the UK. They can barely afford food, let alone insurance, let alone any excesses the insurance wouldn't pay for. Why is is that Americans freak out so much about some publicly funded things and not others? They are aware that major things like the fire and rescue service, and the military, and roads, are paid for by the government, right?
@ezlouie: You say that socialized medicine will lead to a shorter life expectancy. However, France, the UK, and Canada all have government-provided health care. The results are below, with the numbers being life expectancy at birth in years.
Metropolitan France (France excluding territories): 80.7
United Kingdom: 79.4
The British NHS IS a disgrace. So is British Rail, actually - and a few more public services that have been starved to near-death since Margaret Thatcher.
What you don't see is the hidden benefit, maybe that takes a totally different view on social systems. The European way (more or less, more in Scandinavia, less so in eastern Europe) is that we grant a basic level of social security, complete health care and education. There are always people who want more and pay for that, but nobody has to choose - for example - between paying the mortgage and seeing a doctor.
Of course, there is no direct benefit in this system for those who have personal insurance (first-class service...) - that is, IF the alternative is that some people would get nothing.
A system that offers basic health care for everybody, payed for by the taxpayers, and allows people to "leave" it for an insurance with better service, definitely costs MORE.
You only think you pay less. You do not see the large hidden costs, in your taxes and corporate taxes. The Brits and Canadians have discovered the 'benefits' of gov't-controlled medicine: long waits, denial of care, shorter lifespans, preventable deaths, a lack of access to diagnostic equip. and surgery, and a huge, unsustainable cost imposed on their economy. This is why they come over the border to find care here in the US. This is why the British PM just called the NHS a disgrace.