Most large companies have 13 numbers because that allows them to direct your call to different places at different times and according to load and according to where you are calling from. Also they do make money out of 13 calls as the call revenue is shared between them and the telephone carrier. However if you are overseas you can’t directly dial Australian 13 numbers (except, perhaps via Skype) so you need an Australian local number to call those companies.
Also if you have a home phone plan with free national calls it is very likely that your 13 calls will not be free.
Also, even though 13 calls are often advertised as “local calls”, or “toll free” they are not free and on land lines they are charged more than local calls.
As the companies often do not publicise their local numbers but will provide them on request, how about we build a register of these numbers on this site? I don’t know how to go about creating such a resource but as a starter I have 40 large company numbers to offer if somebody can direct me how to get the ball rolling in getting such a resource established.
i worked at a telco and 13 calls were all at a local call cost, now the basic telstra plane has them listed at 40c
https://www.telstra.com.au/content/dam/tcom/personal/help/pd…