The way copyrights have been set up is that the rights that are granted are good for a number of years past the author’s death. Creative works are generally thought to be created by real people. It wouldn’t make sense in a macabre way to have these rights terminate when the author dies, since they can be quite valuable.
On the other hand, another motivation for such a rule is also presented: this way artists can provide for their family and children after their death; the heirs inherit the copyrights and can enjoy some income from the license fees for some definite time after. Many careers, types of work, and businesses are like that: an “asset” is built up over time, which can be passed on independently of who started it, with much effort, presumably.
So a taxi driver might pass on their business when they cannot work anymore, or a plumber. For the taxi driver, the asset would be the business licenses and the car, for the plumber mostly the list of clients, possibly the store. It’s not completely fair, in a way, since a bus driver wouldn’t have much to pass on, or a teacher.
Nevertheless, you could agree that artists should have something similar, although it is still difficult to make it work, see this techdirt article, Rethinking Handing Copyright On To Heirs Beyond Death, for example.
I find this interferes with the heir-motivation. Here’s my thinking:
When I buy let’s say a book or music CD, it comes with copyrights, and these rights are set to expire. At the time they expire, my heirs will have rights with regards to the book or music CD. Be it to publicly perform the work, to reproduce it, distribute it, or create derivative works. All those rights are taken away by these extensions!