To avoid bias? As in to be completely unprepared? Wouldn't reading the résumé give you a better idea of the interviewee's background, and allow you to better assess him?
I'm not following. Why would someone read the resume to someone else?
There's actually not a whole lot of reason for me to look at their resume. The group who makes hiring decisions has it, so my interpretation of it won't be that valuable. Potentially I could ask them to elaborate on some of their prior work or projects, but that's usually less meaningful than just asking technical questions.
(Not trying to claim that I'm actually able to figure out much of anything in a technical interview, but that's the goal.)