Patents are an entirely different arena. If someone patents, say, a specific kind of hinge on a laptop, everyone else has to pay to use that hinge or anything derived from it. In the case of creative works, I can literally take the story of Lord of the Rings and replace the names of the characters, alter a few descriptions, put it in a new world, shuffle up their misadventures and be pretty much free and clear. Just ask Terry Brooks. The few exceptions (such as Harlan Ellison's successes suing various highly profitable film producers that admitted to cribbing from him) prove the rule. The burden of proof that I stole that creative work is so high it is nearly impossible compared with looking at two mechanisms and seeing that they work similarly.Jack Kirby can't save some of the money from the first 70 years and put it away in a trust fund? Patents don't last longer than 14 years and they can be even more profitable. The patent system created because inventors were holding back their discoveries for fear of getting robbed, not because of some sense of indefinite entitlement for the exclusive rights to an idea to be traded around like a commodity a century later.
Look at all the people who are still exclusively profiting off intellectual property of the deceased artist. It isn't the grandchildren of the artists, it's the shareholders of the company.