some, not all, states have the ability to review your vote after your ballot has been counted. this was done as a way to improve transparency in the voting process.

some states may not do it due to increased costs or delays in ballot reporting. some may also not do it because they are actively breaking voting laws by changing your ballots. transparency is best for both citizen and state, pressure your representatives for voter transparency.

What about chemical methods? Traditional film isn't electrical or mechanical, and you could probably make it work with a pinhole camera and your finger.

Why is the law written that specifically? Seems unnecessary.

If you're putting a paper ballot into a machine, the machine is just counting. The paper ballots are retained for hand recounts if necessary. That's different from casting your actual vote on a machine.

That's why the current gold standard is a machine that marks a human-readable paper ballot, and then a drop box, and then a separate machine that reads and counts the ballots. At all times, the physical manifestation of people's votes sit in a guarded box, as piles of physical ballots that can be read and counted by humans, if necessary.

The initial ballot marking machine is good to have because it can prevent overvotes (marking more options than allowed, invalidating the ballot) and can make sure that voters intend their under votes (marking fewer options than the maximum allowed, such as when someone intentionally chooses not to vote on a particular item). The 2000 election taught America what can go wrong with ballots physically marked by the voter, even through a punch card machine. Even since then, there's been issues with what to do with stray marks or incomplete markings on optical scanned ballots (akin to Scantron tests when I was in school).

And once the ballots are marked, it's convenient to have reliable machines count the votes on the ballot. That way vote reporting is quick.

But the paper trail itself is the most important. It has to be a human readable ballot that the voter can visually verify before dropping it into the ballot box.