Oh windytoo..
I do agree that the experts in engineering and airframe design are the best people to assess the actual damage to aircraft there are some precedents which make your logic most uncomfortable.
Challenger space shuttle for a start. O rings which were stiff and amenable to bypass gas when cold. This knowledge was available prior to the flight but was not acted upon by political, managerial and financial pressure. Does that sound familiar? I strikes a definate chord with me in the volcanic eruption saga.
If you wish to compare flight safety in the way you do then you accept the lowest common denominator of safety. If 100,000 people died each year in the UK because of aircraft accident then no one would fly. Is flight safety paramount or something that can be degraded?
Of couse life is a risky thing since birth but risk evaluation depends on known factors or trust. In real life people evaluate risk against benefits. I am not forced to get on any aircraft but that is an absolute. If I do not get on an aircraft then me dying in an aircraft crash is minimal ( but not impossible- the aircraft may crsh into me on the ground). I choose to pay the fare and get on an aircraft because I want to go somewhere of benefit to me. Its not an absolute, its a spectrum of risk. Am I prepared to get on an aircraft not only with the risk of it crashing but me spending days or weeks at great cost not being able to get back to home?
In the past two weeks I have put a plain sheet of A4 paper on my patio table, and guess what - ash deposits. Not every day, but enough for me to wonder what is really up there. I'm no engineer and I have no idea if the accumulated dust on my little A4 amounts to a signficant engine-failing quantity but it makes me think.
The difference between "could " and "will" is easily quantified. Its Murphy's Law.