"Most people will notice when they're standing at a checkout queue buying coffee or whatever, when someone's playing with cash and counting out 10 cent coins, it just takes forever, right?" he said.
"So that's bad for business. It's bad for everyone else."
However, digital payment networks aren't immune to outages, whether they be local or national.
Recent data from PagerDuty found that system failures and outages from telcos, financial institutions, airlines, and other essential services cost Australia $5.3 billion last year alone.
But Holden added that cash's future is hanging in the balance because of Armaguard, the struggling cash-in-transit company that's responsible for transporting about 90 per cent of physical money around the country.
It was brought back from collapse last year thanks to a $50 million deal organised by key stakeholders, like supermarkets, the banks, Australia Post, and others.
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They recently renewed that deal, but Holden said this has raised questions about whether this bailout becomes an annual issue to deal with, or if the government needed to step in and take control of the company to ensure its survival.
If that avenue was taken, Holden suggested something that would likely kick up a lot of fuss.
"People should have to pay extra to pay with cash," he told Yahoo Finance.
"If there was a 1 per cent or 2 per cent surcharge on using cash, they'd go nuts, but that's the economic cost of having cash. It's not a sustainable business anymore."
The professor added that it's also a pain for many businesses to carry and accept cash.
"They need extra insurance, they need to have a float at the start of the day, they need to bundle up cash at the end of the day, and take it to a night safe or take it to the bank," he said.
"It's a giant problem and it's expensive."
Reserve Bank of Australia governor Michele Bullock said in December there would be "very big backlash" if a cash surcharge was introduced.
A BCG report last year found there was a 3.9 per cent cost per transaction for dealing with cash at the point-of-sale (POS) for businesses, compared to just 1.8 per cent for card payments,
Not only that but, Holden said moving solely to digital payments could disrupt the black market and raise billions of dollars.
How does the black market play in the debate about cash?
The criminal underworld and those wanting to dodge their tax obligations typically deal in cash or cryptocurrencies that are tough for authorities to track, according to Holden.
The UNSW Professor said this problem would largely be overcome if cash was taken out of the equation and businesses were forced to only take digital payments, which have a much bigger and easier-to-trace footprint.
He estimated that a fully cashless society could generate $6 billion to $10 billion in additional tax revenue per year, as there would be a huge lift in income and GST tax collection.
Some cash proponents claim physical money allows them to have some privacy against financial institutions and other authorities, even if everything they are doing is legal and above board.
But Holden told Yahoo Finance that if you have nothing to hide, then you should have no problem.
"The government can't just commandeer your bank records without probable cause, but the banks know all kinds of stuff about you already," he said.
Could cash be wiped out before the end of the decade? Professor Holden believes it could only take three years. (Source: Getty)·Francisco Martins via Getty Images
How long could cash have in Australia?
Holden suggested it could be as soon as three years before cash was taken out of circulation, but admitted that was just a "ballpark figure".
Under his proposal, the $100 note would be removed first, and then the $50 note would suffer the same fate a year later.
This would keep going until even the humble $5 was no more.
Taking away cash would be a fairly drastic move, one that hasn't been done by any nation on the planet yet, but Holden said it was a commonsense move.
The Professor also understands the gravity of the suggestion and said he has received death threats in the past about his views on eliminating cash.
It's unclear yet what those services will be, but it's largely expected to be places like supermarkets, petrol stations, medical centres, mechanics and other similar resources.
Cafes, takeaways, bottle shops and hairdressers could be exempt.
When the government announced its intentions to change the law, it said roughly 1.5 million Australians use cash to make more than 80 per cent of their in-person payments.
Treasurer Jim Chalmers said cash can be not only a payment method, but also a "lifeline" as it can be an "easily accessible back-up in times of natural disaster or digital outage".
Holden claimed there are Australia Post kiosks in nearly every town or area, and those could be amended to help those who rely on cash transition to digital payments.
He added that in times of natural disasters and other calamities, many stores aren't open anyway because there's no electricity.
Additionally, he said many digital payment terminals can still accept card payments during network or power outages thanks to their Electronic Fall Back (EFB) mode.
This allows the terminals to store the payments internally until it can reconnect to the system and those payments will be properly processed.
'Cash is here to stay': Banking boss back physical money
Outgoing Australian Banking Association CEO Anna Bligh hit back against suggestions that cash's days were numbered.
"No bank thinks that cash is a thing of the past, cash is in decline, but most banks believe it’s going to be around for a very long time, in smaller amounts, but people are going to still want it," she told 2GB Radio.
"They’re going to still need it, and that banks will certainly be in the business of providing it."
Bullock was a bit more frank in her assessment of cash's timeline in Australia.
“Cash is going to be around probably for another 10 years," she said at a parliamentary hearing in February.
"We’ve got to find a way of moving to a new system that means that distribution of cash can be undertaken and viable.”
