With the paper ballot system, it didn't matter how old or how educated you were - you could tick a box, for the love of god. With the old system, if everything screwed up, there was a paper trail to do an audit. There was backup.
Yes, there are a lot of voters to manage in the US (something like 170 million). Yes, our world has been vastly improved in recent years by advancements in technology. And yes, quite often it's been proven a good idea to make our paper procedures electronic.
So far there have been 100,000 complaints about the voting machines: Reports of e-votes simply "vanishing" into thin air; Cases of voting machines recording thousands of "phantom" votes in Washington DC; "Cranky Voting Machines" recording the wrong candidates in Colorado, Tennessee and Texas.
Not to mention mechanical problems with machines not starting up, printers jamming, tabulation machines not counting votes accurately, and "parallax" - where light affects the layout of the screen, making it difficult to see which part of the screen you're touching and therefore causing inaccurate voting.
Sometimes, despite all good intentions, the old school way is better. And when it comes to determining the leader of the most powerful country in the world, it's necessary. There's no room for error. Because the paper ballot didn't give us technical glitches, it couldn't be hacked, and it didn't cause fear and suspicion. And paper ballots didn't ever turn an election into a voting fiasco.