Syag: Because both of them are promoting justifications that are not grounded in reality. Boys display sociopathic behavior up until marriage and then become kind, sensitive snowflakes? If you don’t have a boyfriend before marriage your reward (seriously?!) will be this awesome guy who will love you and be devoted to you for all eternity–just by virtue of you being such a good girl? In my (humble and inexperienced) opinion, this is not the type of thinking that fosters healthy marriages.
All that is beside the fact that the actual problems with having a relationship outside of marriage are hirhur, negiah, and etc. Would two well-adjusted thirty year-olds be allowed to have a romantic relationship? What is the point in building spurious and potentially harmful ideas? If a girl has trouble accepting the basic halacha as it is, try to find her other emotional (or dare I say, intellectual) outlets.