In the old days, the families of deceased celebrities had limited options about how to continue earning money off the celebrities. The families could license the image or likeness of their celebrity family member for all sorts of memorabilia, books, posters and other things.
However, there was no realistic way of using the celebrity to create truly new work.
Things are different today.
Computers can now be used to make it appear that a deceased celebrity is alive and acting in entirely new movies and television shows, as the Hollywood Reporter discusses in "Carrie Fisher, 'Star Wars' and the Legal Issues of Dead But In-Demand Actors."
This creates an entirely different problem for celebrities to worry about: how they might be portrayed in future movies and what that might mean for their legacy.
For example, an award-winning actor might not want to appear in a bunch of B movies after passing away. There is no way to make sure that does not happen, without planning.
Under current law, the actor's estate could sue for any improper use of the actor's image or likeness, but that does not stop the estate from agreeing to uses the actor would not have wanted.
Because of these new technological challenges, it is important that celebrities also think about their legacy when creating their estate plans.
Reference: Hollywood Reporter (May 1, 2017) "Carrie Fisher, 'Star Wars' and the Legal Issues of Dead But In-Demand Actors."