It is difficult to maintain one build system, let alone two - especially
if one build system is known to be better maintained and the other build
system continues to be used - with bug and feature requests raised
against it.

The maintainers are aware that there are people using the CMake system,
but believe that the extra maintainability of only having one build
system, combined with the knowledge that the current CI system
demonstrates that all supported architectures are working with the
Makefiles make the use of these Makefiles a more sustainable direction.