We have to report large amounts of cash exchanges to try to control money laundering and profiteering from drug sales and other illegal activities. I think the requirement to report cash transactions is very good and it has eliminated some of the banks that specialized in working with money laudering and some businesses in the business of money laundering.
The second reason for these laws is that it reduces the huge amounts of taxable transactions done with cash by people avoiding taxes.
Just answering that question. Not getting into the rest of your cash and government issues as you and I obviously sit at opposite ends when it comes to cash transactions. While you may do everything legally and still prefer cash, it's also the preferred way of doing business for those involved in illegal activities.
As a totally separate issue, I don't like carrying large amounts of cash around, prefer not to make myself a target as I'm seen flashing bundles of cash while making payments. I'm not going to carry enough cash while boating to pay $15,000 for fuel or pay a thousand dollar restaurant bill.
Most cash I've ever handled was when the company I worked for had cargo planes and only on rare occasions made runs to Europe for existing customers. There they had to pay cash for fuel which meant carrying over $100,000 cash with them. Made all of us most uncomfortable.