A women having a lover was grounds for divorce, along with it being a criminal offense. Women in those societies had little rights. They had the lowest places in the family and community. It was quite common for a poor father to sell a daughter to a rich man to be a concubine, to get money to take care of the rest of the family. There was also many women who were forced into being concubines simply because a rich man or ruler liked the way they looked.
Concubinage still exists today in various forms.
Women are not forced into it like they were, and it is still mostly among Asian wealthy class. Having a concubine or mistress is accepted as part of the culture in Asia. The role of women is still second to that of men. Wealthy business leaders hold women today. These women are kept in separate homes or apartments today, and do not work as slaves around the house with the wife.