Maybe there is something about the agricultural tractor (or similar industry) sector where the amount of research and development, manufacturing, sales, support

Maybe there is something about the agricultural tractor (or similar industry) sector where the amount of research and development, manufacturing, sales, support investment it takes, on top of the sales prices/duration, customer dynamic, product lifecycle, etc involved means that the few players who can do it need to earn some margin through service to stay alive profitably. Of course, maybe they're just money grubbing capitalists. But I think there's more factors than meets the eye, and this behavior is not without cause. Otherwise, as you say, plenty of players should be clamoring to offer a fix-it-yourself brand that people would flock to and be loyal to. Maybe sometimes there are real reasons for the way a market and a product are structured.