Because parents would then have to pay someone to babysit and then take their kids to school at the later time in addition to after school care. And why can’t parents go to work later? Same reason companies aren’t allowing work from home even though it’s proven that the majority of people are more productive. The managers need to justify their existence, so they have to have their employees all there at the same time. And for some reason society has decided that morning people are somehow better than everyone else.