But DB .... I is not 100% with you .... 5-6 hours a day! How cushy, let's all join this club!
Whereas in your area probably with multiple customers, the operator may wish to work the backside off of you because Commercial only costed it with 4.2 pilots per aircraft - so year in year out 8 hours a day is draining.
Other areas / contracts around the world may be one single customer for shorter periods and so a higher daily rate may be acceptable. Surely it is, as someone intimated, beholden upon the Ops Manager and Safety Man or equivalents to manage the fatigue risk and be .... open to frank and honest reporting between customer and operator.
I have yet to be convinced accidents / incidents are mainly with a contributory factor of fatigue? Boredom and complacency more likely.