You're fiancé has good reason to be afraid of marriage.
50% of marriages end in divorce
75% of divorces are initiated by women
Men almost always lose custody of their children
Men pay 98% of all alimony and child support payments
If men are unable to pay alimony/CS they are put in jail
Women, having freed themselves from traditional gender roles also freed men from being responsible for women. Under the "no-fault" divorce system, either partner can leave the other for no reason whatsoever. However, the courts almost always side with women when it comes to child custody and spousal support cases. The result is that divorce is incentivized for women and men have strong incentive to avoid marriage if they care about their financial future.
In a world where the gender pay gap is a myth (YouTube: Warren Farrel - Wage Gap Myth), and women have all the same opportunities as men if they make the same career choices, there's no reason to invite state law into your relationship. It can only bring heartache.