The Electoral College was originally set up to protect against too much democracy. The Framers of the Constitution did not want the people to vote directly for the president because they wanted the president to be relatively immune to pressure from the people. They wanted the president to be able to do what was right rather than what was popular.
Today, the Electoral College no longer serves this function since electoral votes are given out based entirely on the popular vote. Today, the Electoral College exists mainly because of tradition. It is unlikely ever to be abolished, though, because the small states would never ratify an amendment abolishing it. The Electoral College gives smaller states more votes than their populations warrant because each state, no matter how small, has two senators. This means that every state has at least 3 electoral votes even if it does not have 1/150 of the population of the US.
People who defend the Electoral College argue that it maintains the relevance of the states. They argue that presidential candidates would ignore small states if it were not for the Electoral College and that they would not tailor their appeals to the people of specific states. In this way, the Electoral College is seen as something of a bulwark of federalism and the power and importance of the states.