Quite a number of years ago it would be a semi-regular occurrence that aircraft would declare a fuel emergency whilst skepticism was put upon those that did were merely queue jumping.
So the powers that be decided that in the event of low fuel then a PAN or a MAYDAY should be declared and in this day and age we have online 'ambulance chasers' just waiting for a 7700 squawk and the opportunity that lives may be at risk.