In certain cultures, when people reach the age of 60, they're considered venerable and are due a degree of respect from those younger than them. It's this same attitude that motivated people once upon a time to write down their values to be passed on to their heirs.
In recent times, the "ethical will" has been making a comeback. The idea is that after a lifetime of experience, you've got a lot more than mere objects and wealth to bequeath: You've got a point of view.
Your legatees may think they know where you stand on certain issues, but they might be surprised by some of your values. It can be a great gift for them to have a document to consult when they're trying to make a hard decision and miss your voice at the table.