I suspect that even within the confines of a monogamous relationship, that act has little to offer women's pleasure or health. I'm only sorry it took this many replies until someone remembered that men often pressure women into this too.
Porn.
My sons are Marines. They went into the Corp together at 17 and 18 (they are 15 month apart). They are fine Christian men and both are now married. My sons honored and respected women as they should be. I had to sit them both down and talk to them before they left for basic training and explain to them that most of their counterparts would be totally desensitized to pornography and would probably expect them to be as well. My sons were known by their recruiters, fellow recruits and later their Drill Sergeant’s and fellow Marines to never have been sexually active. I expressed to them they needed to be roll models and exceptional Marines as a witness. They did just that and made many friends and several that became Christians in large part to my sons witness to them.
When they returned home from Basic Training and School of Infantry they thanked me for preparing them to confront the scourge of porn.