There are two reasons why it is deemed necessary to have so many steps in the process by which a bill becomes a law.
One reason is the desire of the Framers to avoid having a government that could tyrannize the people or make really bad decisions on a whim. To avoid these things, the Framers decided to create a governmental system in which it would be hard to pass bills. Bills would have to be approved by two houses of Congress (elected at different times and from different constituencies) and then by the president (elected by the country as a whole). This would mean that a law would have to be approved by multiple people or groups, making it hard for laws to pass.
A second reason is responsible for the steps that the bills have to go through within each house of Congress. Bills have to be evaluated and voted on by subcommittees and committees as well as by each house as a whole. The reason for this is that Congress wants to get as much input as possible on each bill. They want each bill to be scrutinized by the committees and by interested parties in the public (through hearings).
Thus, the multiple steps in the process are deemed necessary to get the best possible laws and to prevent the laws from being oppressive.
There are, in theory, ten potential steps a bill can go through before it becomes law. Although a president, a member of cabinet or head of a federal agency may propose a bill, only a member of Congress can introduce it. Once the bill has been so introduced, it is referred to a committee who then carefully scrutinises the bill and determines if it can be passed. If the committee does not act on it, the bill dies.
A bill is often referred to a subcommittee for hearing and examinations. The hearings give an opportunity for the opinions of others to be recorded. Such parties may be experts, members of the executive branch, other public officials and opponents or supporters of the proposed legislation.
It should, at this point, already be evident why a bill has to undergo so many processes. All of the parties already involved at this relatively early stage can scrutinise the bill from top to bottom to ensure that all those who may be affected (which may be the entire populace) by its enactment, are satisfied about the conditions set down in the proposal. It is studied and investigated thoroughly and in its entirety in an obviously democratic manner.
Once this process is done, the subcommittee could propose changes or amendments to the bill and once these are through, would recommend it to the full committee who would then vote for the bill. If the subcommittee does not recommend the bill to the full committee, it dies.
It becomes once again clear why there is a reason for recommending the bill or not. The subcommittee, through the hearings and investigations, may be confronted with problem areas in the bill. Those involved in this part of the process may also reject the bill in its entirety or feel that it is unconstitutional, etc. There may be myriads of reason for recommending or not recommending the bill but at its core will obviously lie the due consideration of all parties and interests.
Should the full committee vote positively on the bill, it is sent to the floor which means that the full committee's vote has decided that it be recommended to the House or Senate. The Members of the House then vote on the bill and it is either passed or defeated at this stage. The bill is then referred to the other chamber who may reject, approve, ignore or amend it. Once an agreement is reached on the bill by the House and Senate, a conference report is prepared which should be approved by both the House and the Senate.
Once the House and Senate have approved the bill in identical form, it is sent to the President who can then sign it and it becomes law. Should the president not act on it within ten days whilst Congress is in session, it becomes law automatically. The president may also veto the bill or he may not do anything after Congress has adjourned its second session and the bill would die.
When the president vetoes a bill, Congress may choose to override the veto and if both the House and Senate pass the bill by a two-thirds majority, the president's veto is overruled and the bill would become law.
It is evident that the entire process involves a system of checks-and-balances. To avoid and prevent the abuse of power or authority, it is essential that all interested parties are involved in the creation of legislation. In a democratic society it is essential to ensure a representative, fair and open process and that the rule of law is adhered to so that all citizens are confident in the knowledge that their best interests are being considered and that, in the end, they are in good hands.