It is expected by Western culture that a wife and her husband should only have sex as partners. This configuration is thought to be the only appropriate one. Whether it's a one-night fling or a long-term backup arrangement, a husband should never get onto another woman's lap when her spouse isn't watching. The wife is supposed to be obedient to her husband and to be fucked by him alone. It is considered taboo and improper for a wife to have sex with someone else or be in a threesome. This is where the amazing XXX category is useful.