Because Conservatives realize that our laws and ideals of fairness and the honoring of laws and contracts, instead of living the law of the jungle, came from Christian civilization and not from atheists, libertarians, or pot smoking hippies. Matt Lewis says it better than I can.
You know the negative stereotypes: Conservatives who embrace both fiscal and social conservatism are either prudes who want to tell you how to live — “bigots” and hate-mongers — or people who derive their policy positions solely from the Christian Bible (which, depending on your views, may seem either admirable or dangerous).
But what is not widely understood or appreciated is the philosophical rationale for traditional conservatism, especially as it relates to creating a strong and vibrant society. (In may ways, this philosophy actually traces all the way back to Aristotle, whom many view as the father of political conservatism. Though he was a pagan, Aristotle argued that political life requires a moral foundation, and viewed the family as the fundamental political element.)
But before we get too deep into that, it’s important to note what conservatism is not.
Liberals tend to set up equality as the highest good. Equality is the end goal of most liberal policy. The conservative asks, “Why does that idea become valued over all others?” Equality is certainly good, but as a highest end and goal, it can lead to devastating consequences.
Likewise, the pure libertarian (as opposed to those of us who have some libertarian leanings) sets up liberty as the highest good. Liberty is the end goal of all policy. The conservative looks to the libertarian and asks, “Why does that idea become valued over all others?” Liberty is obviously a great good, but as the highest end goal, it can also lead to devastating consequences.
The conservative argues that the greatest instructor on what laws should exist in a civil society is human experience. So, it would seem libertarianism hits its own walls when it ventures out of its world of make-believe theories and steps into the world of reality.
Alternatively, traditional conservatives believe the rise and success of Western society was not merely a lucky accident or the result of a couple Enlightenment period thunderbolts, but rather the product of diligent work, trial and error, and human experience — and in may ways the result of Christian civilization.
As such, they argue that preserving a strong moral order — an order that took shape over millennia — is vitally important to a functioning society (including a functioning economic system).