Portugal is a simple country, economically speaking, compared other parts of Europe, and they are definitely not as wealthy as Australia on the whole.
But they have a different culture there - traditionally they had a much stronger use of multibanco, which is their socialist version of eftpos on steroi_s, and much less use of visa/master. Multibanco combines eftpos functionality, with austpost bill pay, bpay, and more - you can recharge sims etc with it! The drawback of that commerce system is its quite reliant on cash and atms - as many português hospitality businesses are little battlers and can't afford to pay bank fees, there was an expectation that people would generally carry cash. As we know now - in the richer countries cash is dead now and visa and mastercard rule the world. Tourists come to Portugal expecting to get a cheap holiday and be able to tap and go - but it's not the same context. There isn't as much of a symbiotic relationship between small businesses and banks where card machines are doled out like candy and businesses can afford it. Don't forget australia is one of the leading cashless societies in the world!!!
At the end of the day, there aren't many countries in Western Europe where you can get such quality food and hospitality for such low prices as in Portugal . Tourism is changing all that, but you should enjoy it where you can, and still consider that locals need to live and get by. Just pull out a few euros from the atm, and you will be fine - just look out for businesses that have a sign 'não há multibanco' - that generally means cash only
