Most people would believe that the purpose of law is to enforce morality.
The very first purpose of law is to sustain the legal system. How it accomplishes it, depends upon the social structure.
As an example, in an aristocracy, the purpose of law is to serve the aristocrats and to maintain their aristocracy.
In the most popular contemporary social structure – that is a combination of capitalism and democracy – the primary purpose of law is to sustain the legal industry. That means – the legal system , just like any other industry, will make all effort to put forth legal practices & laws that necessitate the use of the legal system. This may or may not be in favour of society in general – and in most cases is unfavourable for the members of the society.
As an example, take the case of divorces. In a divorce settlement, you are usually encouraged to get a lawyer, but the interest of your lawyer and yourself are completely misaligned. It is not in your lawyers interest to get you a quick settlement. The lengthier the settlement process, the more money your lawyer makes.
In the case of marital conflict, you need to be aware of the legal system and game theory, and understand to always create strategies that align your lawyers interests with yours. And this usually requires both partners to work together, even for separation, and division of assets. Because Together Is Better.