As far as copyright on the glyphs for the letter font goes, the consumer or manufacturer who uses them, pays or has to pay for their use. I'm sure Microsoft and Apple license the various fonts included in their respective OSes.
Letter shapes are not copyrightable in the US. They may be eligible for a design patent, but that's relatively short-lived. Usually the only protectable thing, especially over a decent timeframe, is the name, as a trademark. That's why Apple's version of Helvetica from way back was called Geneva, and Microsoft's was called Arial.
How about forcing these descendents to donate their parents' assets to the public domain, just like copyrighted works?
We impose taxes on inheritances, because inheritance of substantial wealth is harmful to society. We impose taxes on property, because ownership of large, unproductive estates is harmful to society. We abolish property rights like the fee tail because inalienable property rights are harmful to society.
All property rights, beyond what an individual person can defend from others by force, relies entirely on the willing cooperation of others. The only reason I don't own the Brooklyn Bridge is because I can't convince enough people that I do. But if I were more convincing (or could overcome the force that would be mustered against me if I just tried to block others' access to it), my right of ownership would be perfectly legitimate.
Copyright operates similarly; no author has a right to tell others that they can't make copies, etc. of a work, merely because the author created it. All the author can do is keep the work a secret, if he's worried about that. Or he can convince others to respect his wishes. Just as you might not like to recognize my right of ownership of the Brooklyn Bridge merely because I really, really want you to, so too are third parties unlikely to honor a claim of copyright unless it provides some benefit to them that would not be enjoyed otherwise.
And so the deal with copyright is that we're willing to recognize an author's claim of copyright for a little while, because it seems to be useful to society, but eventually we're going to stop, and instead treat the work as being in the public domain, for the same reason. Authors can't stop that from happening, and there's too little benefit for the public in a perpetual copyright to bother recognizing them. It's a one-sided deal in favor of the public, but thems the breaks.