This is a particularly important function in cases where there is significant asymmetry in transactions, as is typical with large corporations versus many customers making small purchases.
In scenario like that, a defrauded consumer has essentially no recourse, as nobody is willing to take a minor matter to court. Even if they do, they'll face an army of lawyers that will certainly drag out the proceedings until its Just Not Worth It for the angry consumer. Class action lawsuits, the type popular in the United States, are a joke, serving only to enrich lawyers.
In Australia, the ACCC sues or directly penalises corporations on the behalf of consumers. They enforce laws related to things like warranty returns.
They have a reputation for coming down like a ton of bricks on misbehaving businesses, with eye-watering fines for even minor things like putting up an invalid "no returns" policy sign at the cash register.
As a consequence of ACCC's actions, consumer confidence is increased, so people spend more, boosting the overall business activity in Australia. Companies that behave have everything to gain and nothing to fear. Companies that try to rip off consumers are eliminated from the market, so that they can't unfairly compete with law-abiding companies by dropping prices to levels where legitimate behaviour is unsustainable.
An anecdote: A local computer parts store refused to refund my $500 for a new GPU that was faulty. I told them that this was illegal, and they're running the risk of an ACCC fine. They just laughed at me. I did nothing about it, and jumped through the hoops to return the card to the manufacturer instead. Someone else must have reported them for their behaviour, and next time I was there I noticed a prominent sign at the cash register saying that they've been fined by the ACCC $750,000 and that they had to display this sign to notify customers of their rights. For a local, small business retailer this is a brutal fine, but they're still around and now they provide instant refunds for DoA parts without argument! Plus, the look on the face of the manager who refused my warranty claim was priceless. The system works.