It seems like there's an implicit theory here: if one maintainer says no, then some other competent maintainer will pop up to handle the excluded bit of functio

It seems like there's an implicit theory here: if one maintainer says no, then some other competent maintainer will pop up to handle the excluded bit of functionality in a separate library. Why would that be the case? And what about the alternative of getting that person to participate in expanding the existing project?