I said “mostly a US thing” for a reason! Australia is definitely one of places where credit cards are more common. Still, from what I checked now, only around 50% of adults in Australia own a credit card, let alone use one.

In US they are popular becase they give lots of rewards (which may be the case in Australia, you definitely know better than me). These rewards come from charging credit card fees to merchants. In the EU the law protects merchants from unreasonable credit card fees, and without charging fees, there are no rewards. And without rewards, there is no point in using a credit card day to day - leaving it only for emergencies, etc.