I agree Japanese teeth are a problem. To me a girl with bad teeth is a turn-off. I googled "Japanese teeth" with an interesting article. It can be found at http://web-japan.org/trends98/honbun/ntj981004.html.

"Crooked teeth have not always been considered a drawback in Japan. In fact, the "double-tooth" look caused by the overlapping of two front teeth in the upper jaws is considered cute in children and young women."

"Many women seem to find their improved appearance worth the time, money, and pain that accompanies cosmetic treatment. One dentist concurs, observing that bad teeth can be a source of stress. Many Japanese women who unconsciously cover their mouths with their hands when laughing may be uncomfortable with the appearance of their teeth."

I'm guess Japan is still in the transition into focus on straight teeth. I also must be uncool in high school to get braces, and very expensive so Japanese opt to get it fixed later in life. It takes longer to straighten teeth once they have set in by age 25 or so, however...