This is a misconception. In totalitarian countries, yes, the government can do whatever it wants and extort money, labor and other favors from the people by sheer force. But in the US, we control the government (we can get into notions like tyranny of the majority or regulatory capture, but for the most part the government is very limited in what it can and can’t do or else the people go on strike). In other words, the US government is the largest union (in the labor sense) in the history of the world. We all pay our dues in the form of taxes and get rather remarkable protections, such as a military industrial complex larger then the next dozen or so countries combined and a level of trade that lets the vast majority of the population veg out on reality TV.
I may personally agree with libertarians that the current system is far from ideal. But where we critically disagree is that a private system would ever come anywhere close to the level of civilization we currently enjoy. If you read the Declaration of Independence and the Constitution, almost nowhere do they talk about economics (other than taxation without representation etc). That’s because a wild west style free market is the most basic form of trade above barter. We see it everywhere, from third world villages trading with one another, to banana republics, to the startup community. It doesn’t need a specific mention, just as we don’t need to bother saying the Earth is round or gravity exists.
The free market is the basis of economies, just as evolution is the basis of the laws of our universe.
So trying to place it above things like human rights or progress in things like public health or education is just bizarre. The idea that we’ll stop paying taxes and turn every road into a toll road, charge tuition for public school, or fight the bad guys with our own handguns when they come surging over the border is.. sophomoric. And what really sucks is the more libertarian a stance the population takes, the more we see concentrated wealth and power undermine the public good, as we just witnessed in the midterm election. Why would we elect people to office whose campaign slogan is that government is bad? That’s like hiring an undertaker as your doctor. Yet we see it over and over, to the point where ideology is given equal weight to pragmatism.
So to get to the point of why paying taxes for government space exploration is a good thing: because if we didn’t, we would be paying the entirety of our incomes as debt service to a central private bank that spends the money suppressing us (the end result of global fascism). We lucked out that a slight majority of the founding fathers were more in favor of government by the people (wherever that may lead) and were willing to fight and die for that rather than fall back to the default position of oligarchy that previous governments had used for thousands of years. Yet here we are again, where wealth inequality from free market policies has reached such a degree that the scales might tip back to a government that only serves the financial elite.