Without trust ...
... We would sink into anarchy.
The AEC seems to forget that. You'd think, after the recent WA debacle, that it would be uppermost on their collective minds ... but the AEC seems to think that 'it's all OK now, the electorate trusts us, the politicians trusts us ... she's apples.'
Wrong. Trust is something you build and reinforce constantly.
And I'd like you to imagine what happened in Republican governed Florida to Al Gore, and in subsequent elections in the same state, when their electronic voting machines proved to be less than fair and correct in registering the results and calculating the vote.
Now imagine that happened to the AEC ... following on the disasters that have occurred with the manual system in a number of electorates of late. And if public trust in the AEC evaporates, so does trust in the election results ... and I'll leave you to imagine what that could do in the increasingly fractious and politically divided country that Australia has become over the last 10 years.
The smart move by the AEC would be to release the code for review ... the stupid move would be to withhold it. Because if they did, and if mistakes and errors, or, even worse bias and corrupted process, were subsequently proved or eve just suspected in the electronic electoral process ... I doubt the AEC would survive.