After a brief lesson in economics — which is most likely to be ignored by those most in need of heeding it — Kevin Williamson notes that the tweaks and adjustments that central planners make to running systems are not light in their effects:

… It’s easy to say: Well, we’ll just raise the retirement age, or cut benefits, or means-test them, or raise taxes on the wealthy who receive them (which amounts to means-testing, but Democrats like that version better). And, yes, that probably is what we will do, eventually. But that does not get us out of the economic pickle: People have been making decisions for years and years — decisions about saving, investing, consuming, working, and retiring — based at least in some part on what are almost certainly faulty assumptions about what sort of Social Security, Medicare, and other benefits they will receive when they retire. When those disappear, a lot of consumption is going to have to be forgone — and a lot of capital dedicated to producing those goods and services for consumption will be massively devalued. Businesses will have to retrench, probably in a way that is more disruptive and more expensive than the housing-bubble recession necessitated.

A core reason that conservatives prefer natural mechanisms (such as price in the marketplace) to regulate human society, with slow, “soft” influences through culture, is that human decisions can be made rapidly and based on factors that have little to do with the topic at hand. One can look at the current landscape for retirement, say, and plan and predict, and while surprises and errors are always possible, at least there isn’t the possibility that a one-party government will force through legislation that changes the entire regulatory and budgetary landscape.
My assertion may jar against assumptions that government programs ensure a baseline benefit that recipients, providers, and everybody in between can count on, but that’s only true to the extent that government can find the resources to fulfill the expectations better than can individuals operating on their own behalf. When government fails to do so, it must take money from elsewhere — in huge quantities — often entirely unrelated to the service and bound up in the plans and expectations of others.
Moreover, as we learned with the housing/mortgage crisis, giving markets false reasons to decrease the influence of perceived risk on decisions can be very dangerous.