Simply because for most developers it was faster to just whip up a bash script than to modify the Makefile and understand why their change did not do what they expected it to do. Hell, i've been dabbling in Makefiles for at least 25 years and still have to look up the weird mapping expressions when for some reason there's the "nothing to be done" or "No rule to make target `xxx'".
Its only killer feature is that it's everywhere, ready to be used by any brand new developer without any work. While "Mise", Just or many of the other replacements need stuff installed and/or setup.