Theft of services isn't just about causing unpaid work; it involves intentionally depriving a provider of the rightful compensation for their services.
Both cases are equal in principle.
Theft of IP falls under a different law in the US than theft of something like gym services.
That's disputable by a strict reading of the original copyright law, before it was perverted by those who would vacuum up "IP" solely for the control and for potential profit.
Copyright is ultimately intended "to promote the progress of science and useful arts, by securing for limited times the exclusive right to their respective writings and discoveries". Limited times. "75 years past the author's death" is not in any practical way limited, when none of the people who were alive during or in the years postceding the author may access what should be, at that point, their rightfully publicly owned work. Current copyright terms hinder the progress of human knowledge and creativity. It incentivizes people who get lucky and create the next huge hit, to rest on their laurels for the rest of their life, getting paid repeatedly for the same work, with no incentive to create anything new. At the same time, those who would make a transformative use of a work (that isn't otherwise a fair use) are rebuked.
14+14 is all we need. Anything else is rent-seeking.
Don't even get me started on those in the world who would support perpetual copyright (not that you espoused that opinion, but many do). Fortunately, that one would require a constitutional amendment in the US to be legal.
The dirtiest tactic used in the copyright push was the Berne Convention. It allows countries to throw their hands up and say "sorry, we can't do anything, we have to harmonize the copyright terms", thus making a treaty that effectively supercedes various national constitutions.
It is interesting that the wording specifies “the useful arts.” Perhaps implying the existence of non-useful arts. I wonder what they meant there.
I would include a lot of media as non-useful arts. Like maybe someone could argue that really thoughtful movies are useful as works of philosophy or education. But most movies, especially most blockbusters are basically non-useful, right? They are just for fun. And so shouldn’t be covered by copyright.
From my understanding of it, "arts" doesn't even refer to artistic works, but more the work of artisans, those skilled in a manufacturing craft. By the same token, "sciences" doesn't just refer to the institution of Science, but of all human knowledge.
Never has a copyright infringer been brought up on theft charges.
It is not theft, no matter how much you claim that it is. If I duplicate and distrbute a work you hold copyright in, I have not "stolen" anything from you. I have infringed your copyright.
This is the problem with using "intellectual property" as the terminology. It incentivizes rightsholders to hold the mindset of "ownership", as one does with property. Copyright is a limited term right, after which the rightful ownership of the public enters the picture.
Both cases are equal in principle.
Theft of IP falls under a different law in the US than theft of something like gym services.