I get cash when I know I'm going to be out at a place that has a discount for cash, otherwise tend not to use it for convenience. Since becoming full-time disabled convenience has been an increasing priority as I don't have capacity to do much out. Getting cash can mean needing a support worker take me to a bank too, and as NDIS is getting cut I probably will be doing without that discount to save worker time for more important things, and just using a card to save time.

There are fee-less credit cards available for students and pensioners. I have the pensioner one and only have to pay any credit card fees when making an international purchase (usually games or other downloaded/online content). There are also other arrangements where you can use a debit card without fees or credit cards that exempt you from fees every month if you have enough "points" or whatever.

You should know that the term "legal tender" does not mean "businesses must accept cash payment" - this is from the RBA:

However although transactions are to be in Australian currency unless otherwise agreed or specified, and Australian currency has legal tender status, Australian banknotes and coins do not necessarily have to be used in transactions and refusal to accept payment in legal tender banknotes and coins is not unlawful.

If a provider of goods or services specifies other means of payment prior to the contract, then there is usually no obligation for legal tender to be accepted as payment.