I think you'll find that the assertion that other airlines do not get a MDC is also false. Sure, the LCCs would likely not, but they try to schedule denisty anyway if they are smart.
It is not the fault of the long haul pilot that the company insists on serving many cities infrequently enough to dilute the average daily flying. Schedule inefficiencies can only be fixed by attaching a penalty for failure. On the domestic network it has mostly worked.
Also, and note this well, the cabin crew have enjoyed MDC for decades in both fleets. Yet S/H CSMs were being rostered for single sector flying on weekends recently just to satisfy some poorly conceived KPM. No one has ever entered into a discussion with the FAAA about min daily credits.