Why? Wikipedia is an encyclopedia [1], there is no need to keep the amount of pages low, storage is cheap and no one prints out Wikipedia on real paper.
The "not notable enough" is a real threat to Wikipedia and the future of the project. The German Wikipedia already lost a lot of former authors (volunteers) because of admins gone crazy. They don't want anyone to edit "their" pages, and revert and ban almost every new edit/user. You can read about this serious situation on Heise.de [2]. Read also the 650+ comments of the related discussion [3]. The English version is still better in shape, but it moves in the same direction, unfortunately.
[1] http://en.wikipedia.org/wiki/Encyclopedia
[2] http://www.heise.de/newsticker/meldung/Blutet-Wikipedia-aus-... ; Translation: http://translate.google.com/translate?sl=auto&tl=en&js=n&pre...
[3] http://www.heise.de/newsticker/foren/S-Blutet-Wikipedia-aus/...
Edit: I am not against "notability requirement", with a better balance it's fine. Wikimedia Foundation should have a closer look at the German branch... maybe resetting all "admin" privileges would help?