Best guess: The back end processing is actually performed by humans at the IRS office in DC and the form is simply an online "request" to one of those humans. And the office where those humans work is only staffed from 7am to 10pm EST.
It /could/, yes. But then one has to also understand how govt. IT development works. You only get, barely, just what you ask for, and nothing more. So the likely reason for no queue is that whatever PM was responsible for writing the requirements that the IT contractor developed towards did not think to add a queue for 'after hours' requests.
And now, it is likely without a 'development budget' (as the bean counters considered it 'done' when it met the initial requirements) and with no 'development budget' allocation, there is no way to get a queue added.
Short username the equivalent of a low /. number. Unfortunately, -1 Insightful isn't possible in the more groupthinky HN.