These properties are not inherent in the idea of copyright. They
come from the choices made in writing Title 17 of the US Code
(which has changed the terms often). Both kinds of creation are
covered by the same grant of power in the Constitution. Neither
has to be implemented unless the tradeoff is worthwhile. And the
argument in the case of software has always been difficult (just
review the history of the changes in patent and copyright laws
over the past few decades).
A patent needs disclosure separate from the use of the patent.
A copyrighted writing reveals its "secrets" in its use and needs
no separate disclosure.