It's not like my husband dislikes sex, but we have many cases where we express our affection physically without always going all the way. Sex is supposed to be about procreation. I don't know why people treat is as something that is a vital tool for communication between the sexes. But some couples can have a good relationship without sex. I think that what's important is not whether a couple goes at it, but how they talk with each other.
Sexless marriages are all about husbands listening to what their wives are saying.
For me, taking the sex out of marriage is the first step toward a better relationship. In one sense, sexless marriages are something to be delighted about, because they show women are now capable of standing up strongly against demands for sex. The answer to why couples become sexless is simple. There're so many other enjoyable things for them to do. Sex is something that a couple can be creative with, and share with each other.