Only because they were legislated into wanting it (https://en.wikipedia.org/wiki/Magnuson%E2%80%93Moss_Warranty_Act https://en.wikipedia.org/wiki/Magnuson%E2%80

Only because they were legislated into wanting it (https://en.wikipedia.org/wiki/Magnuson%E2%80%93Moss_Warranty_Act https://en.wikipedia.org/wiki/Magnuson%E2%80%93Moss_Warranty... etc) Prior to being forced to allow third-party repair shops and parts, they would use every opportunity to void warranties and shut down third parties just as tech companies like Apple are doing today. ('So sorry your engine block cracked. You're right, that would be covered under warranty but we see you had someone install a 3rd party radio so the warranty is void...')