Infidelity doesn’t necessarily lead to divorce, there are many factors that determine if a couple can successfully stay together or not. When couples come in early, there are less layers of resentment, mistrust and hurt, so decisions and forgiveness are not terribly traumatic.
However, when couples come to therapy years after their relationship has been hurt, there are also years of emotional scar tissue. Often, people already know they want a divorce, but are scared of the change or don’t want to be seen as the “bad one” who terminated the relationship. Also, even when the romantic love has faded, long term couples are usually very attached to each other. Attachment is an emotional, intellectual and physiological process, so uncoupling after years together is not easy. All of those aspects–heart, mind, body soul and lifestyle– that have been part of the relationship need attention and “uncoupling.”