After a bit of exploring, I think that it’s possible that the existence of this file is not intentional.  Python uses distutils.core.setup to build install most of its own extension modules, and the PyBuildInstall class used for the install command does not disable the automatic egg-info generation.

With the move of packaging into the stdlib and the addition of the superseding dist-info format, such files can be removed in 3.3.  They’re harmless in stable versions, and removing them would require updates to the build tools that don’t really bring us anything.