If you do not have a will, your individual assets are distributed to your closest living relatives pursuant to New York law. This may be contrary to your wishes. For example, if you have a spouse and children, the first fifty thousand dollars and half the remainder passes to your spouse and the rest to your children.
Having a will also allows you to select an executor who will be in charge of your estate and handle your final affairs, as well as a guardian for minor children. It is important to have a will to make sure that your wishes are followed and not just left up to the default.