The investment review process requires that the investor go through a back-and-forth discussion with the government, figuring out what commitments they will make to the government. Through that process the investor is making its case for why the investment is good for Canada.
It's not as if the act has done nothing. You don't need a prohibition of a transaction in order to increase benefit to Canada. In a way it might be surprising, looking at bald numbers, but considering the fact that the investor goes through this process and gives undertakings to the government, I don't think it's incredibly surprising. In the cultural sector, investors have decided not to proceed with the transaction because they know the government won't allow it, etc.