Nice link, Arkie.
I have 2 customers with Craftsman (AYP) tractors who refuse to "take it easy".
One called me when it "didn't cut right". I replaced all of the bent piece's

, but he must've twisted the deck. -The blade tips would not line up. He swore he didn't hit anything. Yeah, ok. He doesn't have a son to blame, but he must know someone who "did" it? He later "fixed" it by not checking the oil and removing the rod from the crank.
On the other, I can see the bend in the deck where it whacked something hard. He never hit anything, either.
A 3rd, with a MTD Bolens, insists on using it as a road grader (I guess). I just replaced the deck on that one.
As far as not working on them, why not? I explain to them that they are designed to cut grass, and aren't of commercial strength. If they insist, I'll keep fixing them. $$$
Some of the bigger AYP decks and all of the John Deere's (that I have seen) are made of heavier gauge steel. I guess when those get hit, something else bends?
People complain about the thinner decks, but when I tell them to take it easy or buy something stronger, they resist.