That's a false analogy. The legal community deals with well-documented, stable, and easily cited statutes. There are strong incentives driving clear presentation of current law. The objectives outlined in the OP would not be served by those incentives, because they are concerned with all government documents, whether they have made their way into law yet or not. Such documents can be unstable and hard to find, so providing clearinghouse through which they can be cited in a time-aware fashion would be incredibly useful for tracking the evolution of proposed laws.