So you can at least do a real check of signatures against signature on record. How many weren't valid? Also, it may pan out that just, you know, somehow they have more "mailed in ballots" then the envelopes for them. Many, many reasons to save them.
Why all the threats and bullying against witnesses and those who tried to stand for conducting elections following the law if your candidate won fairly? Wouldn't a REAL audit confirm that? Why don't you want an audit to confirm the election?