Why would any married woman who wants to remain married put her husband into that position.
IDK, but I lived it personally. I have a few theories (for my personal situation), but I think it comes down to two things; power and lack of care/understanding.
Imagine if we make this about something else, let's say food instead of sex. And further, let's imagine that instead of sex being exclusive to marriage, we make it dinner; after marriage you may only have dinner with and prepared by your spouse.
Given that buildup, I'm a very light eater, I get really nothing out of eating other than "not hungry anymore". I don't like fancy food/dinners, in fact, I'd eat the same thing every day for the rest of my life pretty happily. And I'd eat it as fast as I can so I can get back to whatever it is that I really want to do. For the sake of discussion though, let's say my wife is the opposite, she really enjoys cooking, meals, the experience of eating and dining.
Well, for me, the constraint of "dinner only with my spouse" is kind of a non-issue. I don't really care for it anyway, it's a necessary thing, but not something I revel in. It's just not that big a deal to me, but, to my wife, it is. She likes having fancy dinners and drawn out dining experiences.
Well, let's fast forward a bit to our married life with "mismatched dinner desires". She's often asking "can we go out" (because without me, she cannot have a good dinner by virtue of having make dinner exclusive to marriage), something I kind of view as a waste of time/money and doesn't do much/anything for me. I could be thoughtful and think "it's important to her" and decide to go out to eat 5 nights a week, or I could, which is I think what often happens, start to realize the power that our "dinner imbalance" give me. Sure, we can go out to eat every night, so long as you do XYZ first. I need to be "wooed" into dinner, it's not just going to happen, even though it did in the beginning (because I was trying to impress). The imbalance in our desire for something, coupled with making it exclusive to marriage, gives whoever desires that thing less immense power over the other person. The more imbalanced the "dinner desire" the more power one person has over the other.
And this is basically what happens in many relationships with sex. It's not a total one way street, this happens to women too (I've read it about here), but whatever the gender, the "low desire" partner starts to gain an immense amount of power over the high desire partner. And we hear about it often enough that we don't even think about it, "If he want's "this" he better work for it, take me out, show me a good time, and then maybe". In fact, in the case of sex, the imbalance is so severe that escorts are paid more the most attorneys or doctors to provide the "service".
The less negative (and probably more often true) way to look at this, rather than a willful desire to extract something (choreplay, gifts, emotional closeness, etc) is just a simple dismissal of the desire at all. I think this is more where my wife fell. Going back to the dinner analogy, I'm very "low desire" for food, it's not that I wanted to keep her from having the meal she wants, it's just that it didn't cross my mind and went to bed without eating dinner. It's more "oversight" than it is a conscious decision not to do something to get some result in return. The net result is basically the same but with very different intent. I think this happens quite often, it's certainly happened to me in relation to my analogy, my wife will eventually look at me and say "I'm starving, we haven't eaten all day" and I'll think "Shoot, totally slipped my mind, and I'm hungry too, let's go get something to eat". It's not a willful denial, it's just "this isn't at all important to me, and I forgot about it" even though it's important to you.