>> Basically rent seeking behavior, expecting perpetual payment for work completed in the past (aka passive income)

Sounds like most SaaS companies.

>> Why stop at paintings, what renders a painting more deserving of payments in perpetuity for the author over, say a chair or some piece of furniture. Or a car, or any of the other myriad of goods people make.

The fact that those things can be replicated and/or mass produced? If it was a one-off handcrafted car or piece of furniture then I agree, it should be covered under the same law.