I'm no specialist but i'd say it's for the same reason you can't put a large fan on a sailboat to produce wind that will blow the sail and make the boat go. If the universe (=all matter and space) expands, you can't use distant matter to pull the closer matter away from us because that same distant matter is also in the expansion move. Your theory only works if we consider the expansion as a local phenomena and not something that affect the entire universe.