selfish sex can occur within a marriage, too. Some people firmly believe they have the right to someone else’s body once they are married. Some pastors (ahem) even teach that. I would rather that two unmarried people have sex that honors one another’s autonomy than that two married people treat each other’s bodies with disrespect.
Image source and full article: http://unchainedfaith.com/2013/10/14/the-opposite-of-christian/