Your getting it all wrong. The bargaining chip is getting engaged, for instance, she gets annoyed at his lack of commitment and refuses to move in together or something else like that. Then he could pull that one out, "Alright then, here's an engagement ring. Let's move in together."
From the information she gave in the practice engagement ring post, they are already living together, therefore they are also already sleeping together.
The comment's on that other site were saying that's exactly why he hasn't proposed and given her an engagement ring. They're already screwing and playing house, what else can she offer him to encourage him to agree to marry?
He's already getting everything he wants.
Exactly. I'll add, i don't believe in basing a marriage on whether or not you will finally get laid. What if you're not compatible? What if your hormones are blinding you? What happens if you suffer an illness that leaves you unable to have sex, does your husband just get a pass to leave you because you can't hold up your end of the bargain anymore? That's the deal you made, after all.
Withholding sex is primitively effective but it is a half-measure at best. Withhold the promise of your lifelong companionship, commitment and support--I.e. break up if you don't agree what your long term goals are. Ideally, make this clear before you get into any relationship.
That's where these women make the mistake of staying with someone who says they are apathetic about marriage. If you stay in the relationship despite them declaring they won't give you what you asked for, you signal that you don't really care about marriage, it's optional and really is "just that piece of paper" they keep saying it is.
If you provide an ultimatum and are willing to follow through, you show them that you are willing to provide lifelong companionship, partnership, emotional support and intimacy that you associate with marriage--but only if they commit to marriage. That you don't intend to make a lifelong commitment to somebody if they can't sign a piece of paper, exchange cheap rings, and stand up and make that commitment in front of your friends and family. Which is entirely fair.
Men who get broken up with like this, almost always turn around and marry their next girlfriend within 6-12 months. And it's unlikely she's not putting out, because most people do.
So sex has nothing to do with it. The break up has forced them to realise what marriage really means, and they also realised, surprise surprise, they want it.
Just probably not with you, or they would have realised this a lot sooner.
There's a great book called "Why Men Marry Some Women and Not Others" full of stats and academically conducted interviews with 600 couples about why they got married and how it all came about. Top reason was: the women who get married, are up-front about what they expect from a relationship.
