Our work schedules are largely inflexible because of the need to coordinate with others. A teacher cannot shift their hours unless the students do so as well. The students cannot shift their hours if their parents can't provide care under the new schedule. The parents can't shift their hours if they have scheduled responsibilities such opening stores, making deliveries, etc. In short, a great many jobs require that others maintain fixed schedules in order to operate efficiently, so flexible hours is not a general solution.