I recently meet someone attended a US school still using the quarter system.
I've heard several theories, the most popular being that the semester system is easier for university to administrate. I've also heard it is so the university breaks will line up better with K-12 school break schedule.
No one has ever explained to me why semesters or more efficient, or more family friendly. I only know 1 person educated with the quarter system in the last 10 years. Is there a reason most US universities adopted semesters?