They should be allowed, but if they do, they have to prepare for people not wanting to buy it in stores.
1. They help you come to the answer by showing you the process
2. There are some
3. You usually come to your tutors with questions
Tantalus, Tityos, and Sisyphus are in Tartarus. It was a place for punishing those who have sinned gravely, and those three certainly were sinners in the eyes of Greek Gods.