Only A Guess
My best guess is that this is because far too many Airbus drivers do not thoroughly understand how their machines operate. Responsible men and women that they are, they recognize that they SHOULD know this stuff, and that it has never been taught or presented. @Rick777 (above) got it right IMO, noting that the Boeing system is more intuitive.
To take it one step farther... nearly all pilots with large aircraft experience could safely land a Boeing in a 'land or die' situation. I don't believe that is true with the Airbus method.
At the end of the flying day, there is nothing wrong with the Airbus operating system. The fault lies with the training given to AB pilots - the average Joe (or Mary) simply does not understand enough about how the AB's logic works. No matter the benefits of the many systems and computers, the boys and girls in those two front seats must still have and maintain absolute mastery of their machine. IMO, most who fly Boeings have that; too many who fly ABs simply do not.