The reason to be off by default is that you needed the advertisers and publishers to voluntarily agree to honor the DNT flag. They can signficantlly make more

The reason to be off by default is that you needed the advertisers and publishers to voluntarily agree to honor the DNT flag. They can signficantlly make more money by targeting users based on tracking data (a targeted ad might be worth 10X a non targeted ad). Now you might not like that but, DNT is not a law, following it is completely 100% optional. You could probably even lie and say you follow when you really don't and there is little that could be done (I'm not a lawyer btw). The advertisers agreed that as long as the flag had to be set manually by the user the would honor it. They made that agreement because it would not impact their revenue significantly. It would be very presumptuous to expect them to voluntarily destroy their own business. Because DNT is optional you need the advertisers and publishers to agree about it. So by making DNT on by default in IE advertisers walked away from the agreement and their is nothing we could do to stop them effectively killing DNT. Now you mention most users don't want to be tracked, but what are they getting in exchange for being tracked? If you asked the average user would you allow your self to be tracked online to use Facebook I be most would say yes. How about you allow yourself to be tracked on line for 1 free latte at Starbucks/month? Again I think most would say yes.