Forcing it on them?

So you've been dating the same person for over 2 years and all of a sudden you get bored with them. MY friend said that after these 2 endless years him and his girlfriend broke up. None the less the woman's parents didn't like that she was dating a white man since her and her family are korean. Of course over the 2 years they snuck around and dated, had sleepovers, and saw each other. But at the very end of the relationship SHE started picking out his flaws. Why can't people notice flaws at the beginning of the relationship and just get right to the point? Does it really need to take months to years when finding out things that you don't enjoy about the opposite sex? Or maybe pointing out all these flaws were leading to a mutual breakup? When there's no hope left for the relationship does the man or the woman decide that they get mad at everything little thing that he or she does? If so then why be together in the first place?