The thing is, proprietary applications statically linking to glibc are
highly likely to be in violation of the LGPL. Or how many proprietary
applications do you know that distribute their object files (and/or their
source code) to allow relinking against a modified glibc?
ucLibc has the same issue, by the way. musl (https://www.musl-libc.org/) is
a more reasonable choice for people who want to ship a statically-linked
proprietary blob. And, unlike glibc, musl is also designed for static
linking.