Couple's Therapy can be sought for a multitude of reasons and one member of the couple may be more in favor than the other to seek out professional help. This is not unusual.
I work with couples who are dating, married, same-sex, separating, divorcing, co-parenting, transitioning in some manner—the introduction of a new family member be it a new child, an older parent, an adult sibling, betrayal, conflict resolution, communication difficulties and a myriad of other concerns.
I believe that relationships are 'co-created' by the influence of each partner on the other and on the couplehood of the relationship.
I work from the perspective that couple's therapy is best when short-term, which could be anywhere from 3 to 12 months.