Why? Because systems are predictable and can be replicated.
But wait, isn't that the exact reason why we set up the system in the first place? We want something predictable, something we can simply plug in and make it play; therefore, we created a system.
The problem is, if the system can be replicated, that means it can also be copied by the competition. You are now merely doing what everyone else is doing, which means you're not hiring people who want to change the world. Now you can hire ambitionless people who want to be plugged into a well-oiled machine. Well-oiled machines may be able to move fast, but they are inefficient at solving problems.
What if instead of telling people to "follow the script" we told them to "use your best judgment" or "do what is most helpful for the customer" or "we trust you, go make something special happen?"
Once you have nailed the solution, systems are good, but never let them replace great people.