The intention of this clause is not explanatory, it is restrictive. Congress is only empowered to secure exclusive right to writings and discoveries for the purposes of promoting science and useful arts—no other purposes. In other words, this clause exists specifically to enable the type of inquiry you reference in your last sentence.
Without this clause there would essentially be no restriction on Congress’s ability to establish monopolies.
Though it seems like in practice sufficient motivation is enough to wring extra powers out of the given text. See eg copyright for movies or audio recordings.
Or the monopoly of USPS. (It's a different clause that motivates it, but that clause doesn't prescribe that a government department is called for, nor that it has to be given a monopoly.)
Without this clause there would essentially be no restriction on Congress’s ability to establish monopolies.