3) He’s stuck in a sexual desert
Nobody gets in a relationship to “not have sex.” Even men who date chaste women are at least thrilled by the promise of sex to come. That’s why it’s so strange that some women have come to the conclusion that it’s fine if copulation is going to be a once-in-a-blue-moon event. The “why” is probably something to share with a therapist, but the result is that the partner is going to be tempted to look elsewhere — and what else would you expect? Sex is an implicit promise in a long-term relationship and it may not be good, right, or moral for a man to cheat if his needs aren’t being met, but it’s about as surprising as the sun coming up in the morning.