I would also like to take issue with your characterization that marital sex is something the wife “gives” to the husband. It should be a mutual sharing, not a “giving” or a “taking.” Sex is used as a weapon by women perhaps more frequently; men use other weapons, such as lack of cooperation, verbal abuse directed at a woman’s self-confidence, etc. Marriage is supposed to be a two-way thing in which, ideally, both people are under the leadership of God and strive to honor His creation. The gift of sex is given by Him to both partners.
It’s a figure of speech. Don’t get your panties in a bunch.