Fair enough. But macOS has more users than Linux, and is partly based on FreeBSD. The shell and the userland tools are from FreeBSD. I prefer Linux of course and haven’t used a Mac in years, but I still think it’s nice making scripts compatible with all *nix systems.
For sure. If you get something for free then it is what it is. Some of my scripts probably won’t work outside of Linux but I still make an effort to not use external commands if there’s no need to. I try to use the internal features of Bash as much as possible, mostly cause it’s just faster that way. A consequence of that is that the scripts are at least more likely to work on other systems (that have Bash).