To be honest I'm hesitant to respond to you because of the level of spittle-flecking you're doing in this thread but I would guess that, by virtue of bash being the standard Mac shell and zsh being a close-enough-but-better replacement, the necessary learning has already happened and overwhelmingly more Mac terminal users will be at least functional with it immediately.
Not the OP, but I agree with both of you actually. It's easier in many ways to run a POSIX-compliant shell with a more "familiar" scripting language to bash users (especially when it comes to running existing scripts or one-liners you find online).... buuuut at the same time I think it's pretty clear that fish's scripting language is much more modern and "better" in many ways.
I don't write shell scripts for nontrivial things and it's rare that I see a good reason to, so I'm not sure that moves the needle much. It's 2019, we have other scripting tools, etc.
Hmm, I see your point, but on the other hand: is that really a good reason to continue the status quo of shell scripting if there are improvements to be made?
Being practical about it: if you install fish you can also install bash, and then running a bash script is as simple as `bash script.sh`, so you can have your cake and eat it too.
Although, in this particular instance, if Apple is going to cease shipping bash at all, I can see why this would be annoying out of the box.
