QFT. Kids are no "wonders", family is not "sacred'. It's just your animal instincts telling you what to do, despite your own best interest. On top of that, many people fall for the illusion of happy family others project. I sincerely believe there must be genuinely happy families out there, but let us be honest - how many proud fathers you know who had enjoyed their time with their family every weekend and bragged about their kids left their family for some young slut? I do not want to be that person, I do not want to live in a lie. I accept egocentric, self-centered bastard I am.
Very good point there. It's like religion in the US: when you ask people if they go to church, the majority says they do. If you look at what most of them truly do, then it turns out to be a lie. Like happy families. Sure, everyone says it is great when you ask. But when you just observe, you see many families interact with nothing but fatigue, contempt and mutual hatred on their faces. Putting a brave face on when a picture is taken, obviously.

Another point would be the problem of rationalization. Humans in general have a tendency to rationalize all their choices post-hoc, even their most horrible decisions. The alternative would be admitting they made a mistake and jumping off a bridge. So they lie to themselves to blunt the feeling of their self-inflicted agony.
Not saying happy families do not exist. My parents were truly happy. But from decades of observation I'm sure they were the minority.