A balance between high and low population states. Our founding fathers were smart in comparison of today's politicians. They knew the importance of such a balance. If presidents were elected by popular vote, all a candidate would have to do is campaign in California, Texas and New York and bunk to the rest of the states.
All states should have a say in who is president and not three.
As someone on welfare and food stamps who do not pay income tax have the right to vote. The president is elected through 538 electors who are people chosen by their state parties prior to the general election. The number of electors is determined by the number of U.S. senators and representatives. Of course, a more populated state will have more electors, but all states will have a say in who becomes president and not three states.