Perhaps because the categories had become unwieldy with the huge number of application submissions, Apple has suddenly removed the aggregate categories that combined all subcategories: "See All iPhone apps" and "See All iPod Touch apps."
Per iPhone Atlas reader Craig Crossman:
"Without (these categories), now you really can't browse the entire library anymore, seeing what has just been added, upgraded, etc. Now you are being forced to look at the individual categories making it really easy to miss something. This makes it very hard to keep on top of everything. This is awful. WHY did they remove them?"