Again, not the point. it is all enabled by default unless you manually turn it off, and the wording is not entirely straightforward and up front with regards to what the data is used for and who can access it. All that is buried in the 45 page EULA is "trusted partners", who could be anyone from Microsoft to the NSA to some company that bought or hacked a company who microsoft have an ad partnership with.
The big problem here is that few people understand just how much can be discovered about a person (if the info is disclosed from the large central repository which is a prime target for attack - or used maliciously by a "trusted partner") from the metadata in their content and their habits without even needing access to their actual data.
And once the info is discovered it can be used for identity theft.
And recovery from that is pretty damn hard. Microsoft's liability for any of this? Zero. You're giving microsoft (and others, like google) all your potentially damaging personal data for nothing.
Apple too, though apple is not quite as bad in a lot of cases due to the explicit assurances regarding the encryption, where the keys are held, etc. Though you shouldn't be blindly trusting apple with this stuff either.