We have to remember that that is in the US, not in South Africa where we have a general lack of/in even basic computer skills. Staff turnaround is also huge in government and therefore keeping track of these payments/cards would be a major operation. Governement is actually moving more towards a centralised environment at the moment for administrative purposes.
Using only 'some' ("accredited") suppliers also does not promote the PFMA and PPPFA. Who will make the decisions as to which suppliers to use etc. You are looking at a aministrative nightmare and leaving the door open for even more fraudulent dealings.

Personally i think that it will take a loooong time before anything of the sort is introduced here. It just won't work at this stage.