When people are happy in a relationship, they live in the here and now. If everything is fine in real life, then you just don't see the point in spending time trying to prove to someone that you are happy with your loved one.
Any couple who brings all their disputes and dissatisfactions to the general court does not gain anything from this. Taking out the trash in front of friends is the worst way to solve a problem in a relationship. Such an approach can only exacerbate the conflict.
Happiness is simply about being on good terms with your loved ones.
No one has to prove anything to anyone. People don't use each other to prove how happy, successful, and loved they are. They're together because they want to be, not because of the "marital status"check mark. But, of course, to advertise your personal life or to keep it a secret is a personal matter for everyone.