Sweethearts

You know when there's a marriage announcement or something about a couple, and they say "they were high school sweethearts" or "college sweethearts"?  Why can't other couples be "sweethearts"?  I guess these high-school and college couples are somehow cuter and more aww-worthy just because they met earlier?  What exactly is it about meeting in high school or college that makes us more in love with these types of couples?  That's my thought of the day.