Well, that's false. The actual US Constitution in Article I Section 8 Clause 8 says, "[The Congress shall have power] To promote the progress of science and useful arts, by securing for limited times to authors and inventors the exclusive right to their respective writings and discoveries."
That could, possibly one-day provide public benefits, but it doesn't have to. If public benefits happen, they are side-effects. The purpose is for authors and inventors to have exclusive rights in their writings and discoveries. They are never required to publish or advance anything for the public. This is a private protection not a public benefit for a "specific purpose".
The text you quote is explicit: the public benefit—promotion of science and useful arts—is the purpose. Providing benefits to creators is a mechanism for acheiving that purpose, not the purpose itself. That’s what I said before, and it remains true, and you’ve just quoted the bit of the Constitution that says it while claiming it is false.
At least according to most histories of copyright I've seen. Wikipedia seems to agree:
https://en.wikipedia.org/wiki/History_of_copyright#Early_dev...
No, under the US Constitution it is for a specified public benefit as its purpose, the private benefit is a mechanism to achieve that.
Under the Statute of Anne, it was nominally for creators (but this was lobbied for by printers after the expiration of earlier laws, and they were the prime beneficiaries in practice.)
The earlier laws were explicitly for printers.