2. Those other files don't get installed to the root filesystem on the
systems that we're talking about.
I do not understand what you think I'm referring to and which files you
are talking about.
The way I'm thinking of a root fs is, /bin, maybe /boot, /etc, /lib* and /sbin.
Most junk gets installed to /usr, which is mounted on a separate
partition on the systems we're talking about.
What useless files do we install to /bin, /boot, or /sbin?
In /lib and /etc, some SMALL files that aren't used on every system do
get installed unconditionally. This is an explicit trade-off: the files
are SMALL by definition, and installing them unconditionally means that
we don't have to add a bunch of USE flags, slow down portage, and bog
down users with choices they don't care about. It also means that users
can e.g. switch between init systems or install logrotate without having
to rebuild @world from scratch. Since the files are SMALL, this
trade-off is in everyone's favor.
Your static libraries aren't small, and they aren't ever going to be
useful to anyone. There is no trade-off here.
3. Those other files generally aren't completely useless.
A number of them are in the default installation.
What files in the default installation are completely useless to
everyone? Small files that are useless to EVERYONE are not covered by
our existing policy, so please feel free to drop them in src_install.