The Will is a legal document that serves three essential and important purposes. First, the Will documents who you have identified as beneficiaries in your estate. Second, the Will appoints who will administer your estate after your death by appointing an executor. Finally, the Will documents how you would like your estate to be passed along to the beneficiaries you have identified.
Other items that can (and should) be included in your Will are to identify and appoint a guardian of you children, document investment discretion of the executor, and to set up any trusts to be carried on to care of beneficiaries of your estate.
If you die with out a Will, a situation called intestate, your remaining assets will be distributed by the courts according to the statues and laws in your jurisdiction. This may result in portions of your assets distributed to beneficiaries whom you did not intend to benefit.
The production of a Will can be complicated and writing a Will should be undertaken with some professional advice, particularly if your estate is sizeable or if there are complex family situations that must be dealt with.
It simply makes sense to have a Will.