We're in the context of Boost here and it has great support for Windows. Switching to a build system that doesn't have mature support for Windows is simply a no

We're in the context of Boost here and it has great support for Windows. Switching to a build system that doesn't have mature support for Windows is simply a non-starter for the Boost project. That a lot of FOSS projects (understandably) have poor support for Windows doesn't mean that all of them do. It also doesn't mean there isn't demand for FOSS projects on that platform.