You are completely delusional, at best.
The reality is that 50% of marriages fail. That is a fact, like it or not. Although one person maybe moral and have great intentions, life common sense, and experience, tells us that other may nevertheless fall from grace. Why should the good one get F'ed by giving 50% of his or her assets to that person?
Believing that people should keep their vows, oaths or promises is being delusional? Assuming your statistic is accurate, that means 50% percent of couples do not know how to pick a marriage partner. If you expect your future spouse to "fall from grace" then by all means get a prenup.