I understand that. The reason clock time is changed is so the agreed times of work across society don't have to coordinate. No organization is an island. If school shifts back an hour, but the office doesn't, the disruption for parents is significant.

Suppliers aren't going to shift their hours if their clients don't. Investment banks won't shift if the stock exchanges don't. There'd be no change since nobody could go first.

It's much simpler to decree the change on the clock than try to convince everyone to change their schedules in lockstep.

Again, I don't like DST. I wish my area would stay on "summer time" all year. Basically shift to the next time zone. But DST is better than the ad hoc solution that you're suggesting.