Then why is my attendence still required for 8 hours a day, in a field where working 4-6 hours would not significantly decrease my overall productivity, but increase my well-being and capability to build something on my own.

The limiting factor for productivity in the knowledge economy (or any work requiring creativity) hasn't been time for a while, why do we insist on keeping it where it has been since the tail end of the industrial revolution (or slightly earlier / later, depending on where you are).