Why do people so rarely take even part of the blame for a failed marriage?

When people are asked about failed marriages, I'm always astounded by the adamant declaration that the other person is always entirely to blame. Whether the relationship lasted 2 or 20 years, whether it ended 2 or 20 years ago. It seems there is always only one person to blame for the breakup-- the other person. In each of the relationships I had before my husband, I take some blame for the break-ups. After all, it's very seldom just the fault of one person and there are always things you could've done better. Do all these people truly believe they were 100% victims in all these divorces? Because to my way of thinking, if you don't recognize your faults in these relationships you're destined to repeat the failure.