By pilots with excessive preson-itis, who won't just bite the bullet and decline to fly it sounds to me.
I don't think so, GTE.
What we are seeing is a pilot who sees blue skies (typ. high pressure weather, like we will have this week in the SE UK) as far as the eye can see, then he goes up to say 5000ft, sees blue skies as far as the eye can see, then he goes up to say 10000ft, sees blue skies as far as the eye can see, and (like me and most people with any kind of engineering/technical education) cannot understand the physical mechanism which would result in particles hazardous to his engine(s) being suspended in the air in a sufficient density while maintaining this visibility of 50nm or so.
If people saw brown (or whatever unusual) clouds, they would believe it.
But nobody I know has actually seen any evidence of this ash.
A few people have reportedly seen "ash" on their cars, but a car covered in grit is such a frequent thing anyway.
I have never seen the slightest deposit on my air filter, and I flew ~ 400nm on the "famous Friday" during the first shutdown.
The engine damage reports have never been backed up by any supplementary information on what/where/when etc.
No wonder nobody believes it.