If Apple did that they'd kill the devotion from the development community.
Like with iOS? Hackers will be annoyed, but Apple doesn't care about them when there are more than enough developers who are either in it for the money or who agree with Apple's position.
iOS started off as a closed environment unsuitable for development. As a web developer on the Mac I'm constantly using cross-platform command line programs, system utilities, and other development tools that would never make it through an Apple vetting process. If Apple killed the ability to install those programs in an update, I would absolutely have to abandon the Mac, and I'm sure I wouldn't be alone.
However, from Apple's perspective, if there are "enough" developers who can't or won't leave (because they develop Mac software or iOS software or both), Apple might not care if you do.
Like with iOS? Hackers will be annoyed, but Apple doesn't care about them when there are more than enough developers who are either in it for the money or who agree with Apple's position.