For what its worth, the BSDs do have their own "make"[1]. Its just not compatible with GNU makefiles so for building 3rd party software you often need to install GNU's make on the BSDs.
A big part of it is likely that many components are mostly stand-alone - even things like coreutils can be replaced at will so long as everyone is using POSIX/portable behaviors - but make(1) gets used by every package that you build, so if any of your packages are using GNUisms in their Makefile you need GNU Make. (Of course, you could declare gmake as a build dependency for 3rd party software that you're packaging, but that only allows you to kinda segment the problem out rather than solving it)
i do use BSD make for a lot of components, but yes, there are a few where GNU make is not easily replaceable :) there are plans to change this eventually, but nothing has materialized yet