After you run 2to3, you still have to go through the changes and manually audit them for correctness.<p>Since pretty much everything has at least one print statement, its removal ensured that <i>everything</i> had to be converted.<p>If Guido&amp;co had tried to maintain backwards compatibility, they could have more easily made the important semantic changes (like unicode strings). Users would have been enthusiastic to upgrade, instead of angry that their time and money was being wasted on irrelevant syntax details.