We have a working sed *and* a working m4 on all platforms.
They’re just usually the BSD variants, not the GNU variants.
In fact, all target platforms (Interix to the lowest degree)
are a complete working, usually self-hosted, Unix system.
They just do not include GNU m4. Or GNU make, for that matter
(well, Mac OSX does, but let’s ignore that piece).
That model is *not* broken, and has worked with GNU tools for
several years, but apparently, recently, the GNU vendor lock-in
(something I’d normally expect from commercial/proprietary Unix
makers) got worse. (Not yet at the level of Poettering, but close.)