"Reasonably confident" is a remarkably weak threshold for putting half of one's future wealth on the line. What else does one deserve to get, as "punishment" for not being sufficiently perceptive of a future spouse's character?
Half of your wealth is very very small compared to losing custody of your kids. If she leaves, the legal system will almost always make sure she gets the kids. Unless you have kids, it's difficult to understand how horrible this is for dads.