I wrote this in one take. I post it here with no edits other than one spelling correction.
If a woman can get her man to show him the innermost parts of his emotional world, he is no longer an immediate sexual influence on her. No longer a threat, maybe. He loses power of attracting her sexual interest at the most sincere and natural level. She might want that, because the presence of his sexual influence over her feels dangerous, threatening, or disruptive: maybe she's trying to do other things with her life and the presence of a man who gives off the kind of energy that can turn a woman on is a distraction to her. Or maybe she feels flustered by the arousal of sexual attraction, from programmed shame or suspicion or antagonism or whatever.
As a man might wish to impose dress standards on a woman working closely with him, because otherwise the sight of her will draw disruptive thoughts and feelings of sexual awareness, interest, desire, arousal: so might a woman want to make a man "safe" to be around by laying bare to her perception his secret feelings.
Make someone safe by securing a level of control over them.
A woman who has sexually neutralized a man by getting him to be vulnerable with her now has more power to take the lead, take the initiative sexually. Or to keep the sexual part of their life under her supervision. To control or to lead - maybe she thinks they're the same thing? Do you think they're the same thing?
Leaders vs. Managers.
To control is to keep from deviating from the course you've set, or to keep from escaping from the boundaries where you've put it. A woman who does not wish to be very sexual herself is glad if she can control the sex life in her marriage: it's a way of keeping safety. And telling her husband she would feel more inclined to be intimate with him if he were more vulnerable with her is a perfect way of doing this: it keeps him working hard to get her approval, it puts him in the position where he is more likely to be called on to be apologetic for failing her - compounding even more the uncertainty and passivity that neuter his sexual magnetism. It gives her that safety and control over the use and expression of sexuality in the marriage, and it justifies her in helping herself to his emotional presence and attention. What's not to love?
And after all isn't this the higher law of marriage: to be a communion of emotional intimacy rather than a crude license to fuck? Is she not more entitled to his emotional attention than he is to her sexual attention?
Now maybe a women is more sexually awakened herself, and she still would rather be the one to set the pace, call the tune and shots, lead in the sex life of her marriage. She might have an even easier time persuading her husband that she finds his vulnerability sexy. After all, female sexual desire is not spontaneous but reactive. Maybe she unlocks her own secret door to her solipsistic female sexuality and finds the pleasure of shared expression worthwhile enough to turn herself on and give signals of invitation regularly. I'm tempted to think that in such a situation a husband might as well go along with her manipulation, allow her to take the lead in the sexual part of their marriage. As I've written elsewhere, if she isn't going to start the fun out of a sense of generosity, maybe her own selfishness will produce the side effect of enough sex to please him.
But I'm still suspicious: I suspect that the woman in our second example, the one who's awake to her inner vastness of self-generating pleasure, will not really wish to control her husband's sexuality by making him a toy - unless she's a psychopath or narcissist or something.
I rather suspect that a woman who really owns her own enjoyment of sexual pleasure and knows how to turn herself on would rather be married to a man who she can feel safe with, meaning she can look to him, respect him, trust him to keep himself together around her.
Maybe she will feel safer with him if he is vulnerable with her? She might tell herself that: that's a showing of an urge to control I say. As in: I wish I could peel back all the layers of this human being and find he is no mere human being but so extraordinary, so super-human that I can count myself blessed among women: I got the best one, I got this incredible superman! How safe I feel now, to know that he is mine and strong and gentle through and through.
If you say you want your man to be vulnerable, what do you mean? Do you want him to come to you for comfort? Cry on your shoulder? Act as if he's a little boy and you're his mommy?
Don't you know? Vulnerability is not just admitting to someone that you felt scared, alone, uncertain (as much of a turnoff as those alone may be). Vulnerability includes full-on panic, inconsolable weeping...
and temper tantrums. Yes: the loss of control that makes children lash out in such frightful fits of rage - which the discerning adult can well see are only bluster to make up for their feelings of helplessness - well, that's just it. A fit of shouting and trying to do damage is the most primal expression of vulnerability there is.
Don't call for it unless you're prepared to welcome all of it - including this.