But it seems likely that in the coming years, people will expect Apple's products to include the latest cutting edge AI (I don't mean useless AI shoved into every possible thing, I mean something closer to a useful Siri). Giving everyone else a 10+ year head start on you is not a good position to be in.

If you choose to outsource your AI to OpenAI/Anthropic/whomever, now you're beholden to another (risky), and for a critical feature of your ecosystem that your customers have grown accustomed to and to expect. And it's not just that they might jack up prices on you, but they can just... get acquired, or go bankrupt, or fall behind on model development...