It is not even about understanding. It is about how easy it is to distrust it.
Contrary to what nerds think, the goal of elections isn't to get bulletproof results by mathematical standards. The goal is to create agreeable consent among those who voted. A good election system is one where even sworn enemies can begrudgingly agree on the result.
A paper ballot system has the advantage that it can be monitored by any group that has members which have mastered the skill of object permanence and don't lie. That is not everybody, but it is much better than any hypothetical digital system
Contrary to what nerds think, the goal of elections isn't to get bulletproof results by mathematical standards. The goal is to create agreeable consent among those who voted. A good election system is one where even sworn enemies can begrudgingly agree on the result.
A paper ballot system has the advantage that it can be monitored by any group that has members which have mastered the skill of object permanence and don't lie. That is not everybody, but it is much better than any hypothetical digital system