Imagine you just hired a new web developer, and added him to this repo. His first local repo clone will include 3 entire projects for iOS, Android, and backend

Imagine you just hired a new web developer, and added him to this repo. His first local repo clone will include 3 entire projects for iOS, Android, and backend server, that he has no use for, or should even have permissions to access in the first place. This sounds like a security nightmare, that also significantly impacts local update times and makes for a huge repo.