What work do you think that professors do? They aren't just teachers, they carry out research and are considered experts in their fields. Post docs only do research as they are working to get a qualification - all the teaching is carried out by the professor here in the UK.Most professors dont work anything even remotely like 80 hours a week and delegate a lot of their work to postgrads
When I was a doing my masters, my professor had 6 others to supervise as well as 3 pHD students as well as multiple undergraduate classes to teach, as well as scientific papers to publish and the corresponding lecture tour.
I really respect people like that - their spare time is spent on people like me who most of the time only saw them when things are going wrong.