Agreed.  Jérôme Marant pointed out that including ldefs-boot.el allows
    a "make maintainer-clean" and then a ".configure" plus "make
    bootstrap" on an unpacked distribution tarball.  I think that's a nice
    feature.

In general, it is a good thing to distribute *all* the code that we
normally use for working on Emacs.  We should not remove something
from the distribution just because "ordinary users don't use it".
That goal is mistaken, and people shouldn't try to aim for that goal.