BillyP: I think you are right to a point, but only under some circumstances. First, I totally agree that a good dealer will find a way to make things work. And I do think that it is the dealers job to know what will and will not work. But that only goes as far as the dealer selling a package of products, or selling an implement for a specific product. What about the guy who has an old Ford 8N and buys a modern trip bucket front loader on it. No warrenty on the Ford because it was built 50 years ago, but lets say the front end fails, and the tractor comes crashing down and damages the subframe of that new loader. Is that loader warrenty going to cover the damage caused to the loader because the front end gave away? The example is extreme, but many of us buy equipment over several years, or buy used equipment, or buy from multiple dealers. Your example in your post only allows for the 1 tractor 1 dealer senario, which, while valid in its own right, is very limited in scope.
Like I said, I agree with you within that limited scope, but what about all the other possibilities, in most of those, the owner is the one who is probably causing his own grief.