Good take on sex as a story telling device.
Though some may consider my sex scenes as gratuitous I only put them in as a means of fleshing my characters out further. Just like in life, sexuality in a story tells a lot about a person. It is the only deeply animal connection that we share so completely with another human being.
When you are engaged in sex with someone you both are in a primal connection. In that connection you may find out a lot things. Some things will enhance your intimate love for the person exponentially. Other things may be tells that this person is cut off from love and cannot reciprocate it. That lust is only lust and not love, etc. I use this technique in creating an ironic feature in one of my characters. He talks tough and selfishly, but is totally giving in his love making...because that is his truth. That said, should you want a tip or three on how to 3Dize your characters using sex (how impertinent of me to even suggest such a thing to Your Greatness) I'll be happy to share them. I have made some sex jaded men in here blush with my scenes. Hehehehe.