Yeah, only reason why is because it results in rushing their asses to report, infract, and discipline every little post that can be found can find in order to hope for moderator status.

Rules and discipline are needed, but giving someone a 1 week trial won't deliver accurate results.
All new staff on any site have a mod rush where they just try to do as much as possible.
The active/annoying mod spree would come to a halt after the title was officially received and a week passed.