Having witnessed the divorces of many of my friends and family members I must say the reasons people go in for a divorce can be as contrasting and diverse as the reasons people would get married.
My own parents threw in the towel after being married(unhappily) for 28 years. On the other hand I've seen my cousin and another close friend calling it quits much faster for reasons I can truly say were simply "incompatibility" and may have easily been workable but lacked the enthusiasm and desire from all parties(they confess this themselves,mind you)
Then I've had friends who endured truly nightmarish marriages to horrible abusive people before plucking up their courage and self esteem and going in for divorce.
In all these incomparable situations I can say one thing. The process of divorce, meaning the legalities, is actually far more easier these days.And this can act as a blessing as well as a trial, since for all those people for whom divorces were truly essential you'd get those who'd just randomly marry and divorce at whim. And I mean both men and women.
In a general sense I'd say people approach marriage with too many high expectations and many times get disheartened at the on set of the first trials itself.Many people lack the patience and tolerance required in a marriage.