The Jinn in Islamic and MENA society holds an incredibly important position, and I believe that the existence of the Jinn is a integral part of understanding the process of acculturation and acceptance in the area, and because of this it holds an important position in society. I also believe that it was incorporated into official Islam, because it is such an important aspect of Arabian acculturation.
Throughout some of the readings, Seidel, parts of Firestone, and El-Shamy, we have encountered many aspects of the spirit culture and how it creates boundaries that ,if crossed, would result in a possession, or even that a pre-existing demon or spirit would compel one to cross societies border. Different local traditions would dictate how to take care of this, but it created a sense of acceptance and an excuse for bad behavior.
The Jinn also helped in acculturation of the societies members. If you broke a rule, you would be susceptible to being possessed by a Jinn. These would apply to women talking to strange men, babies being left alone, and basic household cleanliness.
When I lived with my family in morocco, I had a very interesting mix of religious and traditional interactions. My father, Badr, claimed that he was a very orthodox Sunni, he did not believe in the spirits and believed that some Sufi orders threatened the identity of Islam. Even with this, his family still would stress to me to plug the toilet after I used it, make sure the doors were closed, and take my shoes of in the house as they would bring in the Jinn. These are all basic rules of living in a house, but were reinforced with a religious punishment or justification.