Human error is a factor, true, but look at the hanging/pregnant/dimpled chad fiasco; did mechanical voting add ANYTHING to the process other than complication?
Basically, it's easy to dismiss human error as a reason for mechanising the voting process, by the simple mechanism of allowing the interested parties to oversee the counting process.
Works for us. No reason it couldn't work for you.
People don't cost money. They volunteer.
But now big business has smelt profit in the democratic process, and any hope of a simple-but-effective process in the American political system is dead.
Cross in a box, counted by humans, overseen by the interested parties. It's the wave of the future, baby!