The popular voting system is used in many states to indicate the preference of candidates, so that those elected to serve in the electoral college will know what the people of the state want. I have struggled with the concept of the electoral college for years, but I keep coming back, to the point that it is less likely be to subject to fixed elections and it does have the Congress to act as a check on its decisions.
Depending on a popular vote, with each state having different voting laws, voting hours etc. would make it almost impossible to assure an accurate outcome. Perhaps when we get to the point that all voting machines in a presidential election uploads its result to a central computer, which can then be checked against the individual votes in each state, we may be able to do away with the electoral college. However, I do not see that happening anytime soon.