Dead wrong. Almost no one thinks they need a prenup at the time of marriage, because they fail to project forward on a long enough timeline. Relationships can morph dramatically within 2 years, let alone 10, 20, etc. Yours is the illogic that has resulted in financial devastation for many a sorry soul.
Not dead wrong, if you're marrying for tax/insurance benefits and think you need a prenup you probably shouldn't be getting married. Marriage is first, and foremost, a religious thing and if you're going into it thinking "this is going to fail and my partner is going to try and screw me over" you simply shouldn't be getting married.