TAATS has every pending and active IFR flight plan, and receives every forecast (amended or otherwise) and every NOTAM
A lot of domestic flight plans do not have the alternate, if any, on it and as an Approach controller you don't have time to keep an eye on weather/NOTAMs for those alternates that you don't regularly receive at your console. They have to be requested from the system and could be amended 5 mins after you requested it and you wouldn't know. Alternates for Cairns can vary from Mareeba (10mins away) to Sydney or Alice Springs in the wet season.
When ATC did ops control, it included a watch on destination and alternates, If we can't watch the alternate, the company will have to do it, so since they will (should) have the system in place for that, they might as well watch the destination as well.