Build scripts are explicitly called by a user, a git hook is a side effect they've elected to setup. In this case the tool is adding side effects to commands without the user explicitly choosing to have them.
I can see someone downloading a repository, running a few git commands to make a couple of changes and not realising the git hooks have been installed and the behaviour of a command has changed. Once you're near that scenario, you're just opening up security holes rather than fixing them. It'd be better to have a script one can run after a git clone explicitly that is documented in the project repository.
"To setup git hooks to speed up development, run ./init-hooks." is easy, clear, makes it difficult to do it without knowing what's happening.