There are lots of reasons why a will is one of the documents that every person should have. Here are 5 of them:
1) You own real estate. A will can make your heirs' lives easier by avoiding the necessity of a "license to sell" from the court, if selling turns out to be necessary.
2) You own anything in your own name. A will can specify what is done with anything you die owning in your own name.
3) You own everything jointly with another person. A will can specify what happens to the property if that person dies, and then you do.
4) You own everything in a trust. The trust only governs property that has the trust's name on it. If you receive an inheritance, or if you die owning something (like a car, perhaps) that is not in the name of the trust, a will can provide your instructions.
5) You want your body to be cremated. Otherwise, all next of kin will have to approve cremation.
Of course, there are a lot of other reasons why people do wills. Let me know what I left out, in the comments here , or on Facebook.