The funds collected as GST are distributed so that ❝each of Australia’s States has the same fiscal capacity, under average policies, to provide general government infrastructure and services.❞
The states can spend some of the funds it receives in whatever way the state government deems necessary, while other funds received from the Commonwealth are specifically earmarked for certain purposes. Obviously this means there'll be money poured into infrastructure, health, education, policing and crime prevention, roads, and so on.
I know it can be annoying to see the GST percentage of your purchases being carted off to some invisible metaphorical counting house, but if you think of the services and resources available to Australians as being funded in part through GST, I hope you will see that there's a clear link there. Australia's services don't always work perfectly, and there are some examples of dreadful failures in the systems in some areas, but by and large we have amazing resources available to us - much better than in many many other parts of the world.
And... while corruption can and does exist in government and business (as we've seen only too clearly in this entire 2018!), it's still not as egregious as in certain other countries. That too is something we've seen happen this year - Royal Commissions, enquiries, sackings of council members, public embarrassment for corporations, and regulatory bodies getting some tough bites into tough hides.
Re "if it's the seller they are not forwarding it on to the aus govt", as davewil has said it is not the sellers on eBay who collect the GST. At least that should be a bit of a comfort ot you to know that eBay¹ (or if you purchase items being sent via the GSP, then Pitney Bowes² rather than eBay) collect the GST and remit it to the ATO.
¹ eBay collects it because EDPs (Electronic Distribution Platforms) are treated as the supplier (rather than the individual sellers selling on the EDP) under the new legislation.
² Pitney Bowes collects the GST when the low-value goods are being sent to them (providing the use of an address outside Australia to which goods are delivered), and PB as the re-deliverer then delivers the goods to the Australian address. In such cases, the re-deliverer is responsible for collecting and remitting the GST to the ATO under the new legislation.
Do some searching on these boards and you'll see many threads discussing this, as davewil has suggested.
