While launching the first iPad, Steve Jobs said that it fills the gap between a phone and computer. With phones getting beefier and bigger, and a lot of apps reducing the need to go to websites, that gap is closing fast.
You are right, but the number of ad-block users is significant now -- around 20% (accd. to the same PageFair report).
I have also personally seen around 30% users use ad-blockers, for a site with around 100,000 visitors a day. However, most of the audience for that site is people in twenties, so it's not surprising to see higher than average ad-blocker usage.