I think what many of us stumbled upon for most of these websites like this, is that obviously to get to this point we lost the raw lust and passion, but many of these marriages never had enough love in them to begin with.
To get to the point where you don't consider your partners needs, and you aren't giving them the gift of your time and attention it requires a lack of consideration.
Most of our problems are usually simple in nature. For the men and women, its always easier to explain it if you put the shoe on the other foot.