An example: If there were 50 people on a Ship, they can't all be Captain at the same time, can they? There have to be rules on who will be in charge at what time, who will be in charge of the different departments of this Ship: Who will do the maintenance work and when, the housekeeping, the cooking and everything else on this ship. Laws must be made for everything to run smoothly. Not everyone can be the Captain.
In Society today, someone has to run the Government, the Utilities, the Fire Department, the Schools, the Hospitals and everything else. We can't all go and "fend for ourselves".
the purposes of laws is to help maintain and control a country.