And this lovely notion of " no-one has died from flying in Volcanic Ash" is typical Dead Body Economics. have you an acceptable number in your head ...would 200 be a good number or bad number?
'Dead Body Economics', as you call them, are the basis of all risk management calculations where that activity has the potential to be fatal. To be brutal the 'acceptable' number is the point where the costs associated with fatalities become unsustainable. For instance 2,500 road deaths a year is clearly 'acceptable' in the UK or we wouldn't be able to drive. This doesn't stop us from trying to lower the number though.
If the acceptable number was zero then we wouldn't allow people to drive cars, swim, ski or any number of potentially fatal activities.