There are several reasons why marriages fail: people get married because they don't know the difference between love and lust; familial pressures, you just need to get married, society expects people to get married, it's what everybody does, isn't it? And let's face it, divorce is cheap. What's a couple hundred bucks, especially if you're blaming someone else? And let's face it, blame is important. Everyone wants to point the finger at someone else, and even, on those rare occasions when someone does admit to being at fault, there are always qualifications.
Besides, divorces aren't that expensive. In fact, ending a marriage can be a lot cheaper then actually staying together. Marriage is a business contract, after all, in spite of all the romantic trappings used for decoration. If it were far more expensive to get a divorce, I suspect a lot of people would take a lot more time thinking about just what they're planning. Having said such, I think all states should enact a Divorce Tax. If you want to get married, well, that's fine, however, if you want to get a divorce you have to pay a tax. I think 10% of the cumulative gross wages earned during their time of marriage would be a nice round figure. This means that if a couple gets married, and stays married for 5 years, and the total gross wages both of them earned during that 5 years totals $300,000, they they would owe a Divorce Tax of $30,000.
Now I know there are people who are going to say "Holy Crap, that's too much money, I can't afford that." Well, then maybe you shouldn't be getting married in the first place. Commitments should be cheap and in today's world marriage is a cheap commodity just about anybody can afford.