The real reason is to accomodate for parents’ routines. You need the kid in a place where someone can watch them for you by the time you leave for work (or not long after). Plus yeah they gotta learn to follow schedules and have responsibilities and such. Not saying I think it’s a perfect system, I too hated getting off bed early in the morning.
Every good commander knows you never let a platoon run out of crayons to chew on