I would recommend avoiding marriage to people who "don't believe" in NSA oral.
It's not the sex (although that matters), it's a measure of how much your partner cares about your happiness. Even if "there's nothing in it for them".
I don't like NSA sex. It seems unnecessary to prove you care by providing unreciprocated orgasms and endure sexual frustration to the person who says they love.
A measure of how much you care about your partners happiness is the depth of empathy you feel for them. If you know that they don't like NSA sex then out of love, you would not want it either. I don't expect NSA oral from my husband, he couldn't do it. He is always ready to go and I could not bear to leave him frustrated.
When I have sex, we both get something out of it. I don't give bj cold unless I am in the mood and I decide when. We have as many oral sex sessions as he wants but I have had more than one orgasm beforehand. I didn't set the tone for our sex life, my husband did that from the very first.
I don't know why women are expected to perform sex acts sans arousal and then deal personally with any subsequent sexual arousal. It is so easy for the man to give his wife an orgasm first and then get a bj. Why approach her when he is aroused and she is not?
Women should not marry men who expect NSA sex, it's a red flag. If he is self absorbed in one area, he will be in others. Only marry men who enjoy mutually satisfying sex. If he accepts with grace a stand alone bj when you are in the mood and does not feel entitled then he is a keeper.
If he expects service 2 - 3 times a week, run and don't look back. You will not be up to the superhuman task of decades of NSA bj several times a week just to show him how much more you care about his pleasure than you do your own.
Moreover, you won't be able to endure living day to day with an angry man who feels entitled to a superwoman but married you, a simple human woman.