Historical reasons: American society has settled on 40 hours being the appropriate amount of work for the average person. Starting near the beginning of the day

Historical reasons: American society has settled on 40 hours being the appropriate amount of work for the average person. Starting near the beginning of the day at 9:00 meant 8 hours later people would get off at 5:00. I've heard Ford started that convention, but I haven't really researched it. But I think business hours are now very firmly entrenched in American society and that it would be very difficult to change that convention.