The separation of powers is a large factor in why policy is sometimes attacked from a fragmented point of view. This is because there are typically a number of competing theories as to what the best plan of action is, and with the different branches of government (and different ideologies within those branches) having their own beliefs as to what the best move is, legislation that tries to create policy for large-scale issues tends to be done in a watered-down, fragmented way instead of a wholesale adjustment.