Well the only real reason to do it is, as mentioned to prop up the Oxygen levels at night.
During non-photoperiod plants are Oxygen consumers and they also produce CO2 from their metabolic process, exactly as you do. Therefore they compete with fish for Oxygen. At some point in the early morning, it can be that the Oxygen level bottoms out while there is still residual CO2 from the previous day's injection and this is a bad combination.
The disadvantage of night time aeration however is that it off gasses the CO2 faster, so it takes a longer time to raise the CO2 levels prior to lights on, which, of course, is THE most critical time for CO2.
If the fish are suffering then naturally, aeration is the best response. Use of wet dry filters also have an advantage at night because of the aeration inherent in their operating method, but again, that just means that you have to add more CO2 during the day.
One has to observe the fish late at night or early morning to determine if it is necessary to aerate. Look for signs of Oxygen debt, breathing at surface and so forth. Of course you can just aerate from the general principle, i.e, being safer than sorry.
Cheers,