Describe why people believe it is necessary to have a government.

The most common reason proposed for why people need government is that people need government in order to protect their rights.  This idea is often called the “social contract” and it was made famous by philosophers such as Rousseau and Locke.
In this view, people without government would essentially not have any rights that were guaranteed to them.  They might have natural rights, but there would be no one to protect those rights.  You might think that you could do whatever you wanted to if there were no government.  But think about the fact that all the other people would be doing whatever they wanted to.  If you think about it, you will find that only the strongest people would get to keep their rights.  The strong would do whatever they wanted to the weak, perhaps even enslaving or killing them, and the weak would be unable to stop them.  Therefore, you would have no rights unless you were strong enough to protect them.
This is where government comes in.  The government does limit our freedom by telling us that we cannot do various things like use drugs or play loud music late at night.  However, it prevents other people from taking away our fundamental rights.  It prevents them from taking away our life (killing us), our liberty (enslaving us), or our property (stealing from us).  This is why people say we need government.  We need it in order that it can protect our fundamental human rights from other people.
https://www.csus.edu/indiv/g/gaskilld/ethics/sct.htm