Probably because you saw only GNU/Linux systems. Not so. I looked and tried on many systems. BSD, Solaris, ...
As I understand it, mingw is supposed to be providing a reasonable GNU/Unix-ish environment. These days (years), mktemp should surely be part of that. Any shell script that wants to create temporary files safely should be using it, after all. As you can tell, I am not enthusiastic about complicating about our sources with emulating something that is commonly available everywhere but Windows. k
