It is already known restaurants owners are getting in trouble for small deposits. Its not even $10,000 or $9,000 you deposit.. if you happen to make daily deposits of even few hundred dollars you are guilty of "structuring" aka smurfing.
Another thing is to make sure you can track back your physical hoard of cash. My friend's father is in deep explanations with FBI (and over $50,000 in attorney fees) because when his wife passed away he took all the money they hoard at home under floor and put it in the bank. Some $600,000 of it. IRS didn't like that and proving you had a job all your life and you paid taxes on Over $10,000,000 in income did not stop the case.
I mean, why put it back into the system?
It's pretty clear that his wife was right about the financial system.
What are the biggest ones? I don't see any point of physical cash personally but I'm in a country where no-one uses it.
The middlemen by setting costs that include a minimum charge per transaction also make transactions below a certain threshold non viable because the transaction fee would be higher than the actual charge.
Ask all those marijuana shops trying to get bank accounts if they don't have any costs passed on to the customer for dealing with cash.
Electronic cash in the form of cryptocurrency can make money transfer much cheaper than it otherwise would be. It also doesn't require you to jeopardize your privacy every time you form a financial relationship with a new company, as happens every time you use a credit card with a new company. In fact, your privacy is at risk every time you use an identity linked payment system, given the possibility of hacks/leaks.
But to your point, even these laws are part of a new trend. Money laundering is a relatively new crime, and widespread taxation of private transactions only came into force in the early 20th century, with governments around the world instituting income taxation.
50 years ago, almost all transactions were in cash, and the income tax was widely evaded through the use of cash. The government knew very little about what people were buying and how much wealth they had. With the emergence of electronic payment systems, large Trusted Third Parties emerged that collated transactions, and settled them periodically through the respective central bank. These TTPs became gatekeepers and information gatherers, and enabled central authorities to monitor the most intimate interactions of the population - their financial interactions - in incredible detail. Cryptocurrency holds the promise of returning privacy and economic power back to the decentralized distribution that historically existed, but power, once attained, is jealously guarded, and those who have it will likely not want to give it up.