The problem is that using a computer reduces this to a single point of failure. It only takes one hack of the vote counting machine to compromise the whole elec

The problem is that using a computer reduces this to a single point of failure. It only takes one hack of the vote counting machine to compromise the whole election. Even if you use multiple machines, they're probably running the same software and could all be compromised simultaneously. Computers have no morals and blindly do what they're told to. When the votes are counted by a group of humans, one person making a mistake (maliciously or not) isn't a big deal because nobody expects humans to be perfect. There are checks in place to catch those mistakes. It would take a huge conspiracy to compromise the entire system. I suppose there could be a solution in the future, maybe with blockchains or something. Until then, manual counting is the best option.