Could the restriction not be the device owner choosing to use it? If some rando vibe coded an app and the os told me all the things it can access, I'd probably want to trust the developer before installing it. Why do I need to beg Apple's permission to use software better than their first party offering?

Because you made the choice to trust Apple when you bought an iPhone. And while you may make a deep study of who is providing your alternative AI app (is that even possible with openAI or Copilot or Gemini?), the average use will pick something shiny and lose their savings when it transfers their bank balance outside the country.