So...I guess it's mandatory to have a pronoun when you give an order to someone?
It's not .it's mandatory when warten is used. Look at the description with imperative lesson
It's only mandatory when you're giving an order to someone who you address with "Sie". If you address someone with "du", or a group with "ihr", the pronoun is not required:
- "Iss!" (eat!, to someone you address with "du")
- "Esst!" (eat!, to a group you address with "ihr")