but it is beyond your imagination that, just perhaps, the most common problem is that the centre frequency is not available on the ground
That is NOT the problem. An IFR clearance in the states will MOST USUALLY be delivered by the tower at the field. It is HIGHLY UNCOMMON for an IFR flight (and NEVER for an RPT jet-type service such as in some oz circumstances) to not be in contact with ATS on departure (not necessarily the TRACON). In very rare circumstances, pilots may obtain clearance via phone (hence the existence of time-expiry type conditionals).
Do you really understand the differences between oz and the US, Leasled? It certainly appears that you hope a lot of the stuff you post will just "slide by".