Kevin Drum basically agrees with me that the filibuster exists because people in both parties want it to exist. "They mostly don't want to admit it," he writes, "but both Democrats and Republicans have always had an essentially defensive view of the power of government: They're more interested in stopping the other guys when they're in power than they are in getting their own things done when they're in power."
I think this is almost correct. I'd say that centrists in both parties have always had an essentially defensive view of the power of government, and with good reason. The filibuster lets them stop hateful legislation from the other party, but it also keeps them from having to take votes on bills sponsored by the hard-core wing of their own party. Without the filibuster, they'd spend a lot more time choosing between angering the leadership, and angering their constituents. I can't say that Blanche Lincoln and Ben Nelson seemed particularly thrilled about having to take a controversial vote on health care reform without its protection. And I suspect this is why they can't seem to do away with the damn thing.