Why should I have to send all my prints to Bambu when the printer is sitting right next to me? Why do I have to choose between being able to stop my printer remotely or Bambu not tracking my every move, when it's trivial to have both?

it's because you're the product and they want the designs i think

I don't think so. They can already track popularity very effectively because they control makerworld, and they could have Bambu studio, the app, and the printer phone home too. I don't think they care enough about the tiny tiny minority of users running orca with a LAN only printer.

More likely, it's technical incompetence. It's just easier (for their cloud) to send everything through their cloud

I think OP meant designs which are not on MakerWorld. And I think technical incompetence is not a reason here otherwise they wouldn't gatekeep the access so much.