Thus, if they audit they can be sure the ballot was cast by a legitimate voter.
If you don't tie ballots to voters, you go full Florida where they just keep "finding" boxes of prefilled ballots.
You MUST tie a ballot to a voter if you want your elections to have any integrity at all. There is no other way to prevent double voting, voting out of precinct, etc.
Broward county, 2016 election. They found a box of filled out ballots at the airport return in a rental car trunk... never a word about it again. Same county, defying a judges orders, the police stopped anyone from entering/auditing the count under direction of then admin Brenda Snipes.
Guess who oversaw Bush / Gore recount? Brenda Snipes.
What is the definition of insanity again?
A lock generally needs to be stronger than the motivation of a would be thief. In this case we are talking about controlling the disposition of trillions of dollars so there probably isn't a lock in the world that is good enough.
Based on prior stories many of the machines aren't merely not good enough they are quite laughable and indeed often so old that no parts can be sourced anywhere because they haven't been made in decades.
Edit: thanks for all these clarifications!