The only reason for longer crew duty times is for the airline to reduce staff costs:
Instead of 7 or 8 crews per airframe, they might be able to operate with 5 crews per airframe - if they can get the crews to work longer duties.
Why do they want to reduce staff costs? so they can offer cheaper seat prices.
That works until the longer duties start to impinge upon crew health, and crew work-life balance. Many junior aircrew put up with less than ideal - and even downright poor - contract and operating conditions in the hope that they will one day move on to better things. The senior crew generally have much better conditions and work-life balance - part time or cushy rosters for example - which they can do and still earn enough money to support their lifestyle.
So we get junior staff working ridiculous hours and not complaining, and senior staff working better hours, and also not complaining. So nothing changes.
High time for crews to take a stand. Crews - senior as well as junior - need to say enough is enough and curb the airlines back towards more realistic rostering.