That's not true. There are pleanty of situations where speaking from the heart is more important than what the facts are. Facts csn be too clinical, and too harsh. They're not always helpful, and they can easilly make things worse.
Those are muggles. And I doubt those people are as happy as reported. How can you possibly know how they feel? Because some facts in a book said it? Books are fallible. They're written by people with their own opinions and biases. There is no such thing as a book that doesn't have an inherent emotional flaw. If those people have no access to divorce, or counseling, or separation and if they would become social outcasts for admitting they weren't happy then in what universe would they ever admit it? Why would they tell some historian that they hate their life and their spouse when absolutely nothing good could come of it? How many of them were miserable or abused or secretly gay and could do absolutely nothing about it? How would we ever know?
I think you're letting the statistics color your view of other perspectives.