Paper ballots have a much more visible chain of custody than paperless ballots. In my county, from the time voting starts to the time votes are counted, ballots must either be in a locked closet with tamper-evident seals (for example, at night during early voting) or simultaneously in view of both Democratic and Republican election judges.
It might still be possible to interfere with those, but it's much more difficult than electronic voting machines, which can in some cases be manipulated over the internet, or very quickly by a voter who exchanges memory storage units.
It might still be possible to interfere with those, but it's much more difficult than electronic voting machines, which can in some cases be manipulated over the internet, or very quickly by a voter who exchanges memory storage units.