1. You may not be here anymore but you may care what happens to your life's work after you die.
2. You decide who will administer your estate after you die.
3. You decide who gets your assets and how much (and not the legislation in force at the time of your death).
4. You get to plan the way your assets are distributed taking into account tax consequences.
5. This is your chance to minimize the risk of your estate being litigated.