In a community property state like California, marital property is supposed to be divided equally if the couple divorces. A prenuptial agreement can prevent this from happening. Some people may see a prenuptial agreement as a plan to get a divorce, but a prenup may also protect assets if the marriage ends with the death of a spouse.
For example, a person might be entering the marriage with part ownership in a family business that the person wants to keep in the family. This could be addressed in the prenuptial agreement. For people who own their own businesses, a prenup can prevent the spouse from taking half the business in a divorce.
A prenuptial agreement does not just protect against a spouse taking half of any assets. It can also protect spouses from assuming one another's debts. Such an agreement can protect a couple if they move to a different state where laws about division of property differ from the state where they married.
People may also want to consider specifying how they will divide assets they have not yet acquired. For example, they might include a provision in the prenuptial agreement that each person's income or retirement account belongs to that person. However, if one person feels rushed into a prenuptial agreement or did not receive adequate legal counsel, that person may challenge the prenup. Whether or not a couple has signed a prenuptial agreement, they can still negotiate an agreement instead of going to court if both people are cooperative. A judge may need to review the agreement to ensure that it does not violate state law, but the couple may be able to look for other alternatives besides dividing all assets 50/50. For example, one person might take one asset and the other person might take an asset of relatively equal value.