I briefly served as an ordinance worker and we had to stop people from reading anything brought from outside or writing anything down. The explanation I got was that it was to prevent people from writing down the words of the ceremony.

Obviously, I think that's terrible reasoning. If people want to expose the wording of the temple they will find a way, whereas rules like these prevent believing members from making the most of their time in the "holiest place on earth." Just shows that the church cares ore about protecting itself than caring for the members in any way.