I am firmly of the opinion that this "corner the market on service" is not driven by the manufacturer, nor by the government's regulations, but by the dealer principals and management, and has been adopted by dealers following the lead of really big dealerships, with a concern to follow "industry standards". (although some of those "really big dealerships" seem to be packing up their toys and leaving the playground,,, amazing ain't it)
As far as if the training is "expensive", it seems to me that it may actually be a rather small investment in a good tech, when you consider how much a dealer can make from a tech who is billing 95% of their time, without warranty. The cost of the class is small compared to the cost of the tech not billing that few days time to a paying customer, while the tech is 'in class'.