The treatment afforded our Vietnam vets is, and always will be, one of the more disgraceful parts of Australian history. But this has nothing to do with Australians competing at the Olympics.
Generally speaking, our athletes sacrifice a huge amount over a number of years to represent their country. There are some, maybe 2%, who reap reasonable financial rewards for being elite athletes but the vast majority do it at the expense of a social life, job, career, etc. with no or little financial incentive. Another group who make similar sacrifices is the coaching fraternity.