I think societal pressures would prevent a 4 hour workday even if it was more productive for many classes of worker.
A great many jobs are not fundamentally about productivity, for example a store checkout worker, a hotel receptionist and some IT operations work. In such cases the work is more about being available to cover certain hours and respond to various situations.
For such jobs it would become a hassle to swap workers around every 4 hours for no real benefit. Thus this sets a certain expectation for working hours.
If some types of workers were thus given significantly shorter hours within the same organisation there would be envy and shaming and accusations that those workers were not working as hard as anybody else.
A great many jobs are not fundamentally about productivity, for example a store checkout worker, a hotel receptionist and some IT operations work. In such cases the work is more about being available to cover certain hours and respond to various situations.
For such jobs it would become a hassle to swap workers around every 4 hours for no real benefit. Thus this sets a certain expectation for working hours.
If some types of workers were thus given significantly shorter hours within the same organisation there would be envy and shaming and accusations that those workers were not working as hard as anybody else.