Apple had enough experience relying on and being screwed by third parties that they have a built-in allergy to it. They do not like being boxed in and always want to be in control of their destiny.

This would’ve been useful during their bake off where they were trying to choose if they wanted to go with Google, Anthropic, or OpenAI. But even without that, they would absolutely not want to be in a situation where they had to redo everything to get off a bad partner.