Easy answer to that one. Israel was stuck in a losing war which was causing big problems for the Bush regime. Thus the UN was an easy way out. Neither Israel nor the US wants any end to the occupation, so there will be no UN presence in Gaza and the West Bank. The UN does what the US wants, or VETO. That is the way it was set up in 1945 and that is how it works today.
International investigators to probe several cases of Syria chemical attacks (AP)
from the article: Between Jabalya and Bint Jbail