Men's porn serves to arouse men's sexual feelings, and has the by-product of making them less satisfied with any of the real women in their lives.
Women's porn does the same thing, allowing women to indulge in fantasies about some unattainable "perfect" dream man, to the point of lessening their ability to be satisfied with any real-world men around them.
So does women's promiscuity, hopping into the beds of "exciting" men, who would only bother being with them as long as "no strings" sex is offered, thus making them unsatisfied with the set of men who would actually be open to marrying them.