You make an interesting point. I consider the physical reality of the situation called life in America. You might say that people have the right to life. Yet, people have killed other people. Some of those killers are caught, punished, and executed. Some of those killers have likely escaped punishment. So, someone saying that "people have a natural right to life" really don't seem to accept reality. It is the law that makes things real.
I never said that rights can't be violated by someone else but whatever violation occurs doesn't negate those rights. You say the law makes it real well people break the law as much as they violate someone's natural right to live. Does that make the legal protection invalid because some people choose to break the law?
Let me explain it this way: Assume that natural rights exist. Assume that laws don't exist. Someone breaks the natural right of another and "gets caught". What happens? Nothing. Assume that laws exist. Assume that natural rights don't exist. Someone breaks the law and gets caught. What happens?
Natural rights might or might not exist. It just doesn't matter. It matters what laws exist.
If you mean that people commit crimes--violate the rights of others--and get away with it, you would be right. That is precisely why the Founders, to a man, agreed that the Constitution would not work for other than a moral people. But so long as the large majority of the people accept the consequence of unalienable rights, the ones who violate those rights and get away with it will be fairly rare. The law is necessary within the social contract to define what consequences will be imposed for violating the rights of others.
It is important in the interest of preserving freedom that includes life, liberty, and the pursuit of happiness to understand what an unalienable right is no matter where it came from. And then it is important to promote laws that promote those rights.