There are many reasons for couples to attend therapy. It may be down to communication between the two, or lack of. There may be trust issues, money worries, porn, gambling, or other addiction issues affecting the relationship; or a sick child that needs a lot of attention.
Sometimes the empty nest syndrome can leave a couple realising they need to reconnect and get to know each other again. Or they may wish to discuss how they will address certain issues with a child or other showing a united front. It is important to note that all relationships go through change and stress at some stage and it can be a help and comfort to have the support of a therapist.
Even in the event of a couple who have decided to separate, it is good to talk through with each other how and why the relationship ended, so that the patterns are not repeated in the next relationship. A good ending is a good start to a new relationship.