[IntoRain]

Why not? Mods give a chance for non-staff members to make their own modifications and make them public for whoever wants to use it. Open source codes usually get modified by other outside coders, giving the chance to implement new features that meet your needs but might not be likable or needed by everyone else. Even popular frameworks like Laravel get script modifications this way. It's way easier and less resource expensive (adding stuff to database = more space occupied + more queries have to be made to check if a feature being used) to do it this way than to implement an "on/off" feature like what you suggested.
It's easier for the staff (less debugging, less code changes or updates) and for the users