Plus, if you want to intrude physically into election sites, which can and has happened in the U.S., at least you have to have a lot of people involved in order

Plus, if you want to intrude physically into election sites, which can and has happened in the U.S., at least you have to have a lot of people involved in order to do it on a large scale (increasing the chances of getting caught). Electronic voting machines could potentially be compromised in many places by a relatively small group of people, some of whom might not even be in the country.