Counseling does help couples as long as both members of the couple are willing to put in the work required. There have been several studies that support the effectiveness of couples counseling. For example, research on the treatment of couples in distress found that that couples counseling positively impacted 70% of couples who received it.
Counseling isn't easy. It usually forces us to take a hard look at ourselves, our behavior, and our reactions to see how these are affecting the relationship. Some people are afraid to change their behaviors or find it too difficult, but when both partners are dedicated to saving the relationship, they can overcome hardships when given the opportunity.
Couples therapists understand that many of the behaviors that hurt a relationship are unintentional, and they work to help the couple discover how they can change and improve their bond.