I don't know whether he made a conscious or subconscious decision to leave them out, but it's very indicative of his leftist views.
This experiment that is America began with these important words for a reason. Previous to this statement, that we are "endowed by (our) Creator, with certain unalienable rights", rights were something that were granted or bestowed upon citizens by kings, lords, or other earthly rulers. The Declaration turned all of that on its head, boldly stating that our rights are given by God, not by man, and therefore, they can't be taken away by man. The atheistic left would like nothing more than to abolish that idea in the American mind, so that rights no longer become unalienable, but able to be abrogated by fiat, courts, or law.