My hypothesis is that Apple uses 'security reasons' as an excuse for their lack of dominance in voice assistants + machine learning. Siri's suggestions are virtually nonexistent compared to Google, Amazon, or even Microsoft's offerings. Siri's extensibility is entirely local, meaning that all new functions you want to develop for Siri need to be packed inside an iOS app for the user to install rather than a cloud function. Siri's 'app suggestions' to the user are also inferior, usually defaulting to the apps you used most recently.