Why do civilazations have Laws???

During Humanities today we talked about why civilizations have and need laws.
we asked the question "why do civilizations have or need laws?"

I think that civilizations have need laws to protect their people. Lets say that there is no law in Malaysia saying you can not drink and drive. what would happen? Well people would probably drink and drive at the same time, which could mean accidents occurring and of course the person driving, would get hurt. This doesn't only effect the person driving, but also the people around him/her who are driving. All of this would happen if we as civilizations didn't make laws. Laws are also needed to perhaps decide what is right. Governments and every day people use the laws to decide from right and wrong. Even if the country/civilization has laws or not, it doesn't mean they are always fair. This is like part 2 of what we discussed in Humanities. we talked about the Mesopotamian times, the laws that Hammurabi (the king) made, and whether they were fair or not. I personally thought that Hammurabi's code of laws were unfair and not appropriate according to the crime done. For example one of the laws that he made was "if a son shall strike his father the sons hands must be cut of." I thought that this was unfair because no one really knows who did the wrong thing. I mean for all Hammurabi knew, there might have been a good reason for the son to strike his father. I also think that if a son strikes his father the father must either teach him about respect or discipline him, but definitely not cut of his hands. There are many more laws where I think that don't discuss the situation or reasoning of the crime.