I'm sure they could but I really don't think Apple cares. Their product isn't Mac books or iPhones either. It's the apple ecosystem. Itunes, icloud, Siri, home thing if thats what it's called, etc. They want you stuck in it so you keep coming back to give them money. A GPU wouldn't cut it so isn't worth the investment to put on shelves. If you want to use their chips you need to buy their devices and be in their ecosystem.