Bluntly: for the same reason I would not keep the company of Nazis, no matter how soft-spoken or well-mannered. Everyone with lethal political views thinks it's noble, and for everyone's best benefit.

I'm not speaking of libertarians in Slovenia. A Slovenian libertarian might want a more sensibly ordered country. She might want more sensible taxation; less economic nepotism; equal rules for everyone, instead of nationalist protectionism. She might want the country to develop more like Switzerland. That's a noble goal. I don't see anything wrong with Switzerland.

I'm not speaking of libertarian views on personal rights. People should be able to do what they want with their body. There should not be a drug war that incarcerates millions. I certainly agree with that.

I'm speaking of people who think "taxation is theft", and this makes them support an abhorrence such as the Republican "Affordable Care Act": legislation that aims to put health coverage out of reach for tens of millions of Americans with "pre-existing conditions". In other words, those who need health care.

This is to say: Let's not make insurance companies pay for health care of the sick. That would put an inhumane dent in their profits. For the sake of holy freedom – let's let them just pay for the healthy!

American libertarians defend this, and other things. Economically, American libertarianism is abhorrent.

It's not like the Slovenian kind. It's not about relaxing a government stranglehold on the economy. The US government does not have one. It's not about overcoming economic protectionism that disadvantages foreign investors. The US is already the world's foremost destination for everyone's money.

Libertarianism in the US is about dismantling most, or even all of the state, and replacing it with a do-or-die world, with zero institutional mercy. This is proclaimed in the name of freedom; and these views are held mostly by people who can see themselves thriving this way.

The median libertarian is a young white male who is doing fine, and expects to do better. If only he weren't dragged down by everyone else!

Much of it is naivety. Libertarians do not account for information asymmetry, which enables exploitative business models even in "competitive" markets. It does not account for the tendency of an economy to be monopolized by a handful of smartest, best-positioned people, at everyone else's expense. It does not account for how a real anarcho-capitalist world would not be a utopia, but more like Somalia, mostly.

An anarcho-capitalist in the US feels the price of civilization – the taxes, the rules – but he does not see the benefits, because they are ubiquitous and universal. It's like a fish thinking the ocean is oppressing it. It enjoys its brief jumps out of water; so it wants to leave the ocean, and aspires to live in the sun.

Libertarianism wants to reward everyone by their economic contribution – because people espousing these views can make one. But it turns a blind eye to all the ways people are disadvantaged:
  • Genetics. A person may be born chronically ill, disabled, or just plain untalented. Most people's average ability ceilings are unimpressive; these ceilings are limited by genes.
  • Parents. A person's parents or caretakers may be poor, neglectful, and emotionally and/or physically abusive. Any of this can lead to serious developmental derailment. This is a significant cause of mental disorders in adults, and substantially reduces many people's ability ceilings.
  • Bad luck. At any time, a person can catch an illness, or suffer an accident that's none of their fault, and end up paralyzed, disabled, or interrupted multiple times and for different reasons, so that their success is thwarted (e.g. a student's parents die, followed by serious illness).
Libertarianism usually does not offer a response. If it does offer a response, it's social Darwinism. Your parents are dead, or can't pay for your cancer treatment? "Aww, tough luck. I'm sure you'll pick yourself up by the bootstraps! That's what I did. My parents weren't rich. But look at me, doing just fine!"

It turns a blind eye to how, increasingly, everyone will be late to the game. In a mature economy, resources and means of production are already owned. A person who did not inherit assets has no choice but to prostitute themselves – metaphorically or literally – to asset owners for basic resources. This can work if asset owners are in need of labor. But the more the economy is automated, the less work there is. Ultimately, asset owners will need but a handful of employees, with everyone else as surplus.

The main motivator of libertarians appears to be "freedom". This "freedom" appears to boil down to:
  • Freedom of the libertarian to accumulate resources, based on rules of property and trade that favor people like the libertarian:
    • good genetics
    • middle-class parents
    • no sustained strokes of bad luck
  • The freedom to not share any of the accumulated resources unless they want to. If people die or endure hardship because they lack resources, it's their fault. They lost the game of property and trade – which incidentally favored people like the libertarian, to begin with.
This makes the libertarian, ironically, more entitled than people he might accuse of entitlement – people asking for "government handouts". Those who want "handouts" are not looking to have everything handed to them. They want a semblance of basic living. They want sustenance; basic health care; and some kind of opportunity for their children.

But the libertarian wants everything. Because he deserves it, goddammit. He already won the lottery of life in a number of ways, but is not satisfied with a good living. He wants to not be inconvenienced by others, who lost some aspect of the coin toss, and might need people like him to provide. He wants everyone to respect rules such that he, being in a position to do so, can grab everything. Meanwhile, people who are not in that position get nothing, and should be happy to die.

An American libertarian, ultimately, values his convenience over everyone else's lives. This is reflected in their attitude to health care (a luxury!), as compared to "freedom".