[saurik]

Isn't that like arguing that one should code only in the form of polyglots that would run on any major programming language? The reality is that bash itself is both highly portable and already widely ported: in 2017 (or 2007) my bash script will run on essentially as many platforms as your POSIX shell script (including the aforementioned HP-UX: the last time I had access to one of those I definitely had access to a copy of bash; there was no reasonable JVM available!! but I definitely had bash).