Kids fall in love so quick because they have no idea what it is. Many of them get "broken hearted" But in actuality they have no idea what that is either. Love is an intense feeling of deep affection. Youths don't understand the freedom they have without someone. They only focus on what life would be with someone. Even though they don't understand everything. What I am trying to get at is, adults have more experience in the open world and how people grow up to be. Kids are just in school with the same people everyday thinking "hey I'm gonna be stuck with these people for the next 4 years might as well become more than friends"
Get what I mean? Hope this helps!