On my Chromebook, a linux system, the root filesystem is mounted read only. To modify a file in /usr/bin I would need to activate developer mode then remount it rw. I expect this is probably something similar and done for similar reasons.

The big market isn't developers but end users who have no idea how to protect themselves from real threats and who don't use git. And for them sandboxing, signed executables, verified boots and other measures make life far better.

If you are a developer using a Mac you most likely use brew or some sort of vm/container system anyway.