Option 1: you do as told and leave home at 5pm. You spend 40 hours per week exactly, but work is not getting done, so people are complaining about your performance. Your manager is putting more pressure on you, you are worried about getting fired.
Option 2: you record 40 hours per week, but actually work for 80. Sure your home life suffers but at least the manager is off your back. You are getting compliments about performance and vague promises about raise sometimes in the future maybe.
Which option do you think people will choose?