After Joe Paterno's death, his estate was admitted to probate. Typically, documents filed in a court proceeding are public record. If a Will was filed as part of a probate case, that too would normally be public record. However, Joe Paterno's family requested that his Will was sealed, which the court later did. If someone had a Will but not a Trust, I can understand why they might want to do this. Joe Paterno had a sizable estate and perhaps the family didn't want the world to know about his plans for distribution. Recently, Paterno's Will was unsealed. Turns out, Joe had already planned for this eventuality by creating a Trust. Paterno's Will was a typical “pour over” Will, meaning that any asset that he owned that was not already in his Trust was “poured” into his Trust. A pour over Will typically doesn't list what these assets are, but instead functi0ns more as an all encompassing provision by transferring assets that didn't quite make it to the Trust. The meat of Paterno's estate plan and the part everyone wants to see is the Trust. Unlike Wills, Trusts are private and need not become a public record after a person's death.
For more information about trusts, read Richard Keyt's Article Understanding the Significance of Trusts.