Re: Genuine curiosity...
"...what makes people so anti-MS (for this specific thing) yet merrily give their lives away to the others?"
Easy peasy: You can choose what you send to Twitter or Facebook and what you search with Google. There are less "spookey" alternatives to those programs -e.g. DuckDuckGo and OSS social networking apps- but you can't block/evade spyware bundled with the OS, more so when you can't trust MS upgrades. It's like the difference between a turnpike and a band of roaming highwaymen.
To put it short, everything you do with the OS - usually including personal data/intellectual property/sensible information - can be sent to MS to be "monetized", i.e. sold to the highest bidder.