Yes and no. For a normal user sure. In a sensitive network you don't want these data flows leaving your network because you don't control them.Yes there needs to be more controls here. But Cortana is pretty slick and I honestly think that this kind of stuff is the future. Ultimately people want computers to do more and make things easier.
If they do some searching they can easily find downloadable registry files that make turning Cortana off/on a breeze. But the average Win10 user is most likely oblivious to Cortana and other data mining. They just want to browse the web, play games, etc. For those in the dark it's not going to matter.Yes, we can do that. But normal people should be able to do it too, without having to learn how to edit the registry. It's called being user friendly. And there's no reason why Microsoft cannot make it this way, if they gave a shit about their customers. Which, they don't. They have a virtual monopoly. They don't have to. Somehow, they got around the anti-trust laws, and now have so much market share, that it doesn't matter anymore.