I wonder how many people are actually unhappy in their marriages

Something happened today that really has me wondering. My daughter went to stay the night with a friend last night and she came home telling me that she asked her friend’s mom how she met her husband and she told her the story and my daughter told her it was a cute story and the woman said “we don’t really like it.. we are more of just room mates now.” And honestly I would never have guessed that about them had my daughter not given me that information. And of course I basically feel the same way about my own marriage. So how many married couples do we know that seem happy but really at home they are just room mates?