You do, for one. You just don't know it, because you don't think about what you believe. Most libertarians don't.
Libertarianism is mainly an economic ideology, based on laissez-faire policies as espoused by Adam Smith and Ludwig von Mises. What libertarians have done is merely extend such ideas into socio-political strata, in so doing failing to understand the nature of human beings, and of human societies, giving very short shrift to personal responsibility.
Not that I'm saying they're not willing to take on the consequences of their own bad choices (or good choices, for that matter). What I'm saying is they do not promote good choices. They do not promote good behavior that avoids problems.