Very good question, Gorgophone.
The regulators won't take action until there is an accident in which the prime cause points specifically and unequivocally at stress. And even then it is simpler to call it "pilot error".
The airlines won't take action because it is easy for them to address alcohol as a problem - they just install a system of checking pilots' breath before flying. Fatigue is something they really don't want to address, as the only real method of combatting it is to impose harsher limits on pilots' duty hours, thus ensuring they get less work out of each pilot, and less flexibility about how they roster.
Pilots as individuals can do very little at all.
I suspect that this is down to the unions - BALPA, IFALPA, IALPA, VNV etc. The problem with that is that it will be painted in the press by everyone (specifically the more right-wing press, but also pointed that way by the employers) as overpaid, molly-coddled prima donna pilots wanting to work less for more pay.
Perhaps governments, IATA and ICAO should take a lead in this? But they only take action when the regulators advise that action is needed. And the most recent work within the EU on pilot hours would actually have resulted in pilots working more rather than less, resulting in an increase in fatigue.