It's those line deletion/addition ratios man, it has to even out.. or preferably favor the left side. But seriously, it's often said that the tree is now full,

It's those line deletion/addition ratios man, it has to even out.. or preferably favor the left side. But seriously, it's often said that the tree is now full, you need to remove something unmaintained before you add may something new. ..more seriously, while it may not be noticeable by DVCS users, working directory sizes for CVS/SVN repositories can actually /decrease/ when code is removed.