And the main problem with fatigue is that it is very hard to recognise it in yourself, thus people reporting for duty fatigued. And what if you start the duty feeling OK and then fatigue hits you part way through a double night sector? Do you go to the nearest airport, land and call the company to tell them you are not continuing because you are fatigued? I don't think so!!!
I have had countless days/ nights in hotels where I have been woken up by reception/ fire alarm practice/ actual fire alarms/ cleaners etc. despite having posted the "do not disturb" notices. If I am in a hotel it is usually because there is no-one at base to do the flight. Therefore I know if I call in fatigued someone else will get called out, and they won't have had sufficient rest.
And how we are magically meant to switch from an early to a night or vice versa (albeit with usually a day or so in between), and be 100% rested I have yet to discover. I sleep well but sometimes it really is impossible to get a "proper" amount of sleep prior to every duty, due to the way it is rostered (and an attempt to have a life, albeit even with early nights, on your days off).
And there is still a stigma attached to calling in fatigued for duty if you don't manage to sleep well (even if its not your fault).