I only bother voting if there is a referendum or local politician I care about. Neither was true in this election. Living in Maryland I already knew Clinton would carry the state. So why go vote?
I bet there are people like that in deeply red states who feel the same. I bet voter turnout would be higher all around under a Popular vote scenario.
Voter turnout was still low in swing states are well, so I could be wrong. But I think at times people realize their vote is sort of pointless.