Most of what the average working family "has" today are contract assets. What are contract assets? Your life insurance, 401k plan, pension, and IRA are all examples of contract assets. Upon your death, they are paid and distributed according to the terms of the contract, which includes some type of beneficiary election form. Remember filling those out when you started your job, established your IRA, and applied for life insurance? The terms of your will do not control the distribution of your contract assets, even if your will was made at a later date.
So, I'm fine without a will, right? Unfortunately, probably not. What happens if both you and your spouse pass away leaving young children? The court may have to appoint a guardian of their estate to protect them. This can be cumbersome and expensive. Through your will, and proper designations on your beneficiary election forms, your contract assets can be held by a trustee that you appoint for the benefit of your children until such time as they reach adulthood.
Consult an estate planning attorney so that you can harmonize all the elements of your retirement planning and other assets, and determine the best way to pass along what you have worked so hard to accumulate in life.