[L]liberal programs tend to be more permanent. Once they get entrenched, even conservatives are loath to eliminate them. For all the big talk about Social Security in 2005, it wasn't the filibuster that kept George Bush from passing his privatization plan. In the end, he couldn't even get majority support for it.That's Kevin Drum (with my emphasis added), arguing for majority party rule in the Senate on the basis that it would be good for liberals (he also supports it on democratic grounds, but here's he's making the practical argument.
I don't think we know what would have happened to Bush's Social Security plan if we had strict majority rule in the Senate. Yes, Republicans bailed on Bush's unpopular plan. But they knew, once Democrats formed a solid front against it, that the plan was dead. (Could they have passed it through reconciliation? I don't know, but just as with health care in 2009-2010, the obscure rules of reconciliation would have been policy success very tricky). The same, by the way, is true of the Clinton health care plan in 1993-1994. Once it was clear that it needed 60 votes in the Senate and that no Republican would support it, Democrats lost interest. In both cases, 2005 and 1994, the Members of Congress from the president's party were very reluctant to cast controversial votes for a plan that was highly unlikely to pass; indeed, neither bill (if I recall correctly) had a single committee markup. In a 51 vote Senate, it's just really hard to say what would have happened.
As for the larger point of whether a status quo bias is inherently good for conservatives or not, there was an interesting comment thread about it here earlier this week. I think there are strong arguments on both sides.. Right now, I believe that the policy status quo is probably somewhat closer to the ideal point of mainstream liberals in Congress than it is to the ideal point for mainstream conservatives. On the other hand, there's something to the idea that over time, the liberal ideal point changes, and so a status quo bias makes it harder for policy change to match that. On yet another hand, however, I tend to think the nation is closer to the mainstream liberal's ideal point, so one could figure that in, as well.