(not strong arguments but some possible explanations)

1) ./make can be more portable e.g. you might use some GNU Make syntax that does not run on BSD and have to insall gmake just to run that

2) Make is not designed to be a command runner and have to manually add .PHONY to everything

3) case looks minimal and flexible enough (although I'm sure sh's confusing syntax can cause a lot of pain for non sh experts like esac wtf)