The same reason why left wingers believe in Keynesian economics. Political ideologues tend to believe in an economic system religiously, no matter how often it fails. We seriously need to make a new system.
I should probably turn my monitor upside down so that all incoming thumbs downs from...
Did you guys know that Dede Scozzafava, a Republican, was forced out of the 23rd congressional district race in New York because of this? This test is actually spelling victory for Dems because Republicans can't pass it easily.
The current reform they have will just empower the insurance corporations, which is the problem and not the solution. Single payer is probably the best method in the long run, as shown by countries that do better than us in Health Care.