Members of Congress use these techniques because they can, and it is in their interest to do so. The voting sessions contain a small amount of parties which allows the possibi
…lity that members can purchase others members' votes. The most important aspect here is that these votes are kept on public record so it is easy to verify whether someone went through with the agreement. If one member discovers the other did the opposite of what they agreed, they would be ostracized and would have little bargaining power to pass their own measures they are pushing. ( Full Answer )