I suppose there isn't much of a market in general purpose computers anymore compared to iOS devices, but is there another reason Apple wouldn't start an arms ra

I suppose there isn't much of a market in general purpose computers anymore compared to iOS devices, but is there another reason Apple wouldn't start an arms race in specialized hardware graphics chips based on what they are doing for iOS devices? By that, I mean specialized for low power video playback specifically, rather than high end graphics processing suitable for content creation and games.