> I don’t really understand why Apple has to provide a ChatGPT product

Control. It boils down to control. If you own a platform, you want to make your "suppliers" (apps in this case) as substitutable as possible.

If people start associating ChatGPT or Claude or Gemini as the main reasons to buy a phone, at some point in the future, they'll think - gee, most of what I'm doing on the phone is interacting with $app, and I can get the $app elsewhere.