I believe "good girls" are in the same boat as "nice guys" in that they often go unappreciated until later on in life.
Oftentimes the "good girl" and "nice guy" for that matter are introverts who for the most part remain in the (background of social circles).
During high school they're not the cheerleaders, home coming queen, or the leader of any organization. They don't visibly display confidence and they also tend to be more conformist. They obey the rules and never question authority.
Much of our youth is about being rebellious, believing we are adults deserving of all the perks that come with it (without the responsibilities).
The "hot girls" in high school were the one's who dressed more provocatively, openly talked about sex , dated/partied with guys and acted like she was a "woman" among girls. "Nice guys" fantasized about being with her much like a "nice girl" might have fantasized about being with the captain of the football team or "bad boy". The "in crowd" are viewed as real life "celebrities".
Where as the "nice girls" and "nice guys" are peering at them with their noses pressed against the looking glass. It never occurs to them to date each other as they both pine over those who don't acknowledge them!
People want to associate with the "stars" or those who light up the room.
Nice girls don't want to use sex appeal to draw attention to themselves. They may subscribe to the idea of becoming friends and getting to know one another very well before considering to have sex. They may also have a strong religious background and want a guy who is similar or believes in waiting to have sex after marriage. They're analytical about life and the choices they make.
Young men in particular with raging hormones would rather "fast forward" to having sex and being spontaneous in general.
For young guys going "slow" is boring. Sex and parties are fun!
Last but not least "nice girls" and "nice guys" aren't usually respected or admired by the "in crowd". People tend to want to be with "winners" as opposed to "losers" especially during the teenage years and early 20s. If all the "hot girls" or those in the "in crowd' consider the "nice girl" to be a loser or damaged goods then a lot of guys will ignore her.
Eventually as everyone matures most girls let go of their "bad boy" phase and most guys look to settle down with a "nice girl"