No matter what kind of relationship you are in, both parties always have the option of leaving. Wearing a ring doesn’t change it. Getting married doesn’t change it. Signing a document doesn’t change it.

Ceremonies and legal documents can make leaving more difficult - because it creates a risk of social or financial punishment; but whether that’s a good thing is subjective. The people in this comic are of the view that they should only stay together if they both continue to be happy with their relationship. And I think that’s a fair enough perspective. No one wants to be stuck in an unhappy relationship, right?