I’m sure slave owners had an intention to promote progress in agricultural economics. Given that, would the ACLU then say “Oh, well, if it’s to the commercial benefit of the nation, of course you can keep your slaves”?

Let’s look after the individual first, and then, given such security as the state can offer them (instead of jeopardy for infringing commercial incentives granted to corporations), the individual may then be able and inclined to progress science and useful arts (given a market for that kind of thing).

Without the folly of instituting copyright or patent, this is what could have been written:

“To promote the progress of science and the arts, by securing indefinitely to authors and inventors the exclusive right to their respective writings and discoveries until such time as they choose to publish them.”

Sounds just as good. Better still, it doesn’t enable publishers to go around suing random members of the public for enjoying their cultural liberty, and especially not software engineers who’ve unwittingly reinvented three patented algorithms before breakfast.