Because attraction and sexual interest do not line up always.
Colby happens to be together with his spouse for six years. They’ve been hitched for four. He came across his spouse as he was at university. He thought she had been a “smoke show” (their terms). He nevertheless discovers her attractive, specially now that she’s holding their very first son. But Colby is experiencing a puzzling issue: “I have experienced no aspire to have sexual intercourse together with her. We don’t love her any less, in fact I do have more aspire to please her than ever before.