Most Arab men are monogamous, because marriage is expensive. It costs a lot of money to buy & keep one wife, let alone four.
Under Islamic law, a man has to provide equally for all his wives. This is nothing to an oil shiek, who obviously has the money, or a Bedouin, who simply would pitch another tent. But to a middle-class Arab, it is financial suicide.
In Saudi Arabia, as well as other Arab/Muslim countries, it is generally just the sheiks or the Bedouins with multiple wives. Unfortunately, this can create an equity problem, where some guys get all the girls, and the rest are frustrated.