To give individual legislators more opportunity to impact specific policy areas, through committee work. To divide up power within the legislature so that more members have some power or control and influence over agenda setting and legislation. Partisanship shapes committee staffing. Expertise is generally recognized, even among freshmen or new legislators. Committee Investigations Hearings provide information, testimony of experts, and are channels of communications and influence.
Hearings can provide publicity and public exposure.
Hearings can spur new laws, but also expose corruption and illegality. Vesting policy jurisdiction and particularly subcommittees tends to remove that power from the majority political party and the whole chamber Jurisdictional overlap is common, Sometimes committees fight over which committee has jurisdiction over a particular bill. In some instances, several committees have jurisdiction, and the bill has to go through several sets of hurdles just to get to the floor of each house. As the executive branch has grown and policies have become more complex, oversight has become much more difficult. The debate over whether legislators should vote according to conscience or constituency preference has never been resolved.