The position of the constitutional court of Germany is worthy of note
Essentially they say that even _if_ those machines would be "secure", they still couldn't be used as it's not about them being secure, but about the layperson being able to check for election fraud by themselves.
A simple pen an paper system may be easy to compromise, however it's trivial to check. You look into the ballot box before they seal it, it needs to be empty. You count how many people came to vote and how many ballots are in the box when they open it again. Then you make sure those ballots are properly counted and nobody adds or removes any ballots. Since the ballots will be stored in a sealed box afterwards, you can always recount them.
Any sort of system that involves mechanics, electronics or mathematics is much harder to understand. A voting system has to even work in the "paranoid" situation where everybody is against you. You cannot ask a mathematician to proof it's correctness to you, you cannot ask a team of forensic engineers to disassemble and check your voting computer.
Biting the hand that feeds IT
