That's naïve IMO. That's like saying that nobody cares about your email communications or other data. Of course they care. It's part of who you are and to advertisers and corporations, that's very appealing. I understand why they send it to "the cloud" but to pretend like that's not something that corporations would be interested in storing and mining is just wrong (that's like saying, well, you're one in a hundred million, so no one cares what you're searching in Google... which isn't' true... you're a small portion of the pie but they very much care to know what you're searching for and how you're using the Internet).
Yes, but outlook.com for example doesn't look into your emails to target you for adverts.
You can also look at the privacy statement for speech;
When you use the speech recognition service on your phone for speech-enabled features or apps, whether provided by Microsoft or third-parties, your speech input and performance data associated with the speech functionality, such as changes you manually make to text and the final text result, ("speech data") will be automatically sent to Microsoft to process and respond to the request, and to improve the speech service. To better tune our speech recognition algorithms, your recent contact names (but not phone numbers or other contact information) will also be sent to Microsoft. You will be prompted to enable the speech recognition service when you first attempt to use any speech functionality.
When speech data is sent to Microsoft, Microsoft generates a unique ID that is stored on your phone and sent with requests to distinguish requests from different phones. The unique ID is a randomly generated number that does not contain any information to identify you personally. Accordingly, the speech data is not associated with you or your device.
If you disable the speech recognition service, you will not be able to search online using your voice or send a message via voice, but you may still be able to use other simple voice commands supported solely on the phone, such as "Call Mom" or "Start Internet Explorer."
To prevent speech data from being sent to Microsoft, if you've previously enabled:
- Go to Settings > Speech.
- Uncheck Enable Speech Recognition Service.