Microsoft admits that when it switched on "do not track" by default in Internet Explorer 10 back in 2012, it was "welcomed by many." However, the company now has to switch it off to comply with the latest industry standard. The newest World Wide Web Consortium (W3C) draft for the feature says it "MUST reflect the user's preference," meaning you have to turn it on to activate it, just like on Firefox or Chrome. Redmond explains that it has no choice but to change the default, else advertisers can argue that it doesn't have to honor any DNT signal from Microsoft's browser.
While that sounds problematic, note that "do not track" has always been optional: advertisers can choose to honor your request, but they can simply ignore it, as well. This change will take effect when you set up a new computer or when you upgrade to Windows 10, and hence its new Project Spartan browser, after it comes out this summer. Microsoft promises to provide clear instructions on how to switch it on, though, and to make it easy to tweak the setting.
Here's what the company quoted from the new W3C draft:
Key to that notion of expression is that the signal sent MUST reflect the user's preference, not the choice of some vendor, institution, site, or network-imposed mechanism outside the user's control; this applies equally to both the general preference and exceptions. The basic principle is that a tracking preference expression is only transmitted when it reflects a deliberate choice by the user. In the absence of user choice, there is no tracking preference expressed. (Emphasis added.)