Re: Cortana Knows my name...(so does MS and 'partners', uncles, aunts, 2nd cousins...)
Of course the answer to why is Cortana. As fun as conspiracy theories are, I think the simplest answer here is also the most likely to be true.
In order for their digital assistant to work in any half-decent way, it needs all of this information to build up a profile of you.
This does not take in to account the fact that many users with Windows 10 do not use Cortana. I like the ability to set quick reminders by typing plain English, but other than that I have no use for it. I'm not against the concept and can see how it could be useful for some people, but I'm just not sufficiently disorganised that I need a constant watcher to organise my life for me.
I'm okay with this being the price if you really want to use Cortana and enable it to do all the recommendation, telling you about flights, informing you its your wedding anniversary tomorrow and your wife is already pissed off with you because she texted you complaining that you hadn't done the washing up again, but Cortana, along with all the information it needs to work, should have a simple and complete off-switch.
If MS just provide this, all those who hate the idea of MS slurping their data and who don't need Cortana will be happy, and all those willing to pay the data price for having Cortana work will also be happy. Simple.