"the new iWork ’13 apps are not really upgrades from the previous versions. Rather, they are entirely redesigned-from-the-ground-up new programs. Having to make this sort of drastic revision, especially within the inevitable time and resource constraints, almost guarantees that some features will get dropped along the way.
So why did Apple make such drastic changes?"
Good article from Ted speculating on what happened and why. But speculation would be unnecessary if Apple simply explained. http://www.tedlandau.com/slantedviewpoint/index.php/archives/2013/1289