Answer:
The majority of bills introduced to the US Congress in any given year die in the committees, this is simply because most bills that are introduced are not good or important enough to be passed.
Among the reasons that may cause a bill to "die in committee" we have: the bill is uproperly written, the bill deals with an issue that is not considered to be important by the committee, the bill is a duplication of an existing law, or the bill was never meant to become a law in first place.