The Jacob, Rachel, and Leah story is instructive.
Genesis 29:31 Now the Lord saw that Leah was unloved, and He opened her womb, but Rachel was barren. 32 Leah conceived and bore a son and named him Reuben, for she said, “Because the Lord has seen my affliction; surely now my husband will love me.” 33 Then she conceived again and bore a son and said, “Because the Lord has heard that I am unloved, He has therefore given me this son also.” So she named him Simeon. 34 She conceived again and bore a son and said, “Now this time my husband will become attached to me, because I have borne him three sons.” Therefore he was named Levi. 35 And she conceived again and bore a son and said, “This time I will praise the Lord.” Therefore she named him Judah. Then she stopped bearing.
In this case, Jacob is actually banging his wife a lot (well, at least 4 times but probably way more given the statistical amounts of sex needed to conceive). But Leah is unloved because he is just going through the motions with her when his desire is for Rachel.
These days it’s mostly wives giving their husbands duty sex, and it is still a terrible thing. Sadly, I don’t think the husbands and wives that give duty sex know how terrible it truly is for the other spouse.
Such is the problem with only obeying the “letter of the law” like the Pharisees instead of the “Spirit of the law” as new creations in Christ.
1 Corinthians 7:3 The husband must fulfill his duty to his wife, and likewise also the wife to her husband. 4 The wife does not have authority over her own body, but the husband does; and likewise also the husband does not have authority over his own body, but the wife does. 5 Stop depriving one another, except by agreement for a time, so that you may devote yourselves to prayer, and come together again so that Satan will not tempt you because of your lack of self-control.
I’m a firm preacher against duty sex when I am able to talk with it in person with people in real life. Act like you actually care about your spouse and don’t be ruled by your own feelings.