I don't think Apple has missed out on much (yet). The best LLM's (e.g. gpt4o, sonnet 3.7) are no where near being able to run locally and still make mistakes.
Some LLMs can run locally, but are brutally slow with small context windows.
Apple is likely waiting until you can run a really good model on device (i.e. iOS), which makes sense to me. It's not like they're losing customers over this right now.