How does that happen?

Recently Lee and I have discovered that a friend of ours and his wife are, after 12yrs of marriage, getting a divorce. Firstly this is not a friend whom any of our friends know. This person doesn't read our blog so don't try to guess who it is because we have not mutual friends with this couple :) This has brought to my mind a question which I have asked myself a million times before.... How does a couple just fall out of love? Ok yes I know I have been married before so you must think I have fallen out of love before but in my defence I never loved my ex husband in the first place. After 3 weeks of marriage I was at my mom and dads crying that I wanted an annulment. I married my ex husband because I needed a place to live. And wasn't moving in with him without being married. We were only together for 2 yrs and by 2 1/2 yrs we were divorced. This isn't the kind of falling out of love I mean. See I think that love grows everyday and right now after almost 9 years of marriage I love Lee more today than anyday in the past 9 years. I love him more today than yesterday and tomorrow I willove him more than today. Our marriage isn't perfect we have ups and downs just like any other marriage but even in tough times I still love him. I don't understand how anyone just falls out of love. Our friends say it got to the point where they were more like roommates than husband and wife. But how? How could they not talk to each other anymore? How is it possible for a husband or wife to just become roommates? I just can't imagine ever falling out of love. Lee and I always have something to talk about sometimes it is the kids sometimes its about work and sometimes its about.... well I don't know but we always find something. I make an effort a hundred times a day to tell Lee how much I love him. He does the same to me. We have little inside jokes. We send each other emails or txt throughout the day just saying I love you. We both do things to try and make the others life easier. He is always there for me. In fact he is the only person who I feel like I can be myself around. He knows what I need when I need it and I am the same with him. He knows my moods and I know his. We both live our lives to make each other happy. I do everything in my power to make him feel like he is the most important person in the world to me because he is. I can't imagine ever falling out of love with him. And I imagine that if I ever started to feel like what we have is starting to change for bad we would sit down and talk about it and what we can to make things great again. I feel really bad for couples who just fall out of love. Maybe I am just one of the lucky few who is truly married to her best friend.