The ebuild of media-libs/audiofile does not provide itself, but it can, and thus should, as you can see from 'use.desc' (in /usr/portage/profile). If it does, others can optionaly rely on audiofile, and some will benefit. I know there is one such, namely, x11-wm/sawfish. Reproducible: Always Steps to Reproduce: 1. 2. 3.
there is no need to provide itself, other packages can simply depend on audiofile