Except dealers are individually owned and operated franchises....................GM doesnt give two shits about dealers and if the dealers make money or not on anything except new car sales. Hell, just look at what GM pays the dealers for warranty repair rates/claims.
Newsflash, dealers make all their money on selling cars. Not service and parts. Being required to provide service and parts is literally the bane of dealers' existances....just ask anyone who owns a major car dealer. They HATE service/parts, especially if its a warranty job.
So the whole conspiracy of "car mfg's wanting to strong-arm customers into ONLY having work done at dealers" is a crock. As long as the dealer sells as many new cars as possible, thats 100% all GM cares about.
Its cutthroat in the car industry, thats why most car salesmen are sleazeballs...if they dont sell as many new cars as possible, the dealer fires them....if the dealer doesnt sell as many new cars as possible, GM pulls their franchise.