Entertaiment is a great way to relieve stress and get some fresh air. It also stimulates the brain to realease seratonin and dopamine. Entertainment often hits on points that the brain was evolved to react deeply to in order to understand the world. Alot of the themes like backstabbing, murders and other social issues that are in entertainment are the things that humans were shaped to react to.
The word entertainment comes from the Medieval Latin intertenere, from the prefix inter meaning inside, and the suffix tenere meaning to hold. It is closely related to the Indo-European root ten, which means to stretch.