A former speaker of the House of Representatives, Tip O'Neill, once said that "All politics is local." What he meant by this was that politics ultimately relates to what's happening at the local level. Even grand geopolitical concerns relating to foreign policy and defense have local implications, whether it's the stationing of army bases and other military installations or the location of factories for the manufacture of defense equipment.
Electing members of the House every two years is a way of reinforcing such localism in American politics. Members of Congress are required to live in the districts they represent, so they already have a close connection to their constituents. Needing to fight an election every two years concentrates their minds on ensuring that their constituents's needs are met.
In broader terms, this biennial reorganization of the House is useful, as it gives some idea of the political mood of the nation. The House was always intended to be the democratic element in the American system of government, and its being elected every two years allows it to be more responsive to public opinion than the presidency (up for election every four years) and the Senate (elected every six years), but staggered so that only a third of the seats are up for election every two years.