TSSOV
I take your point.
Scenario:
You do your sector from LHR to HKG.The next service back to LHR is not for two days.Two days accommodation,two days allowance ,too expensive.At the end of your 24 hour slip in HKG you pax to BKK,transit for 2 hours and pickup the QF2 to LHR.You have no hours limitation to your tour of duty.Pax operate it doesn`t matter.You have been employed to save money.16 or 17 hour duties will become the norm for you.If you complain or go sick too often your contract will be reviewed.There are thousands of people ready to fill your shoes.I have been in airline management for 20 years,I have a reasonable idea of how these things work .