Can you not imagine legitimate reasons for doing this?
A small business owner makes a deal with a property owner to operate the business out of the property on a payment plan where the profits from the business buy out the property owner over time. The customers of the business pay cash so the business pays cash.
The buyer or seller doesn't trust the local banking system (e.g. because they have seen recent evidence of not being able to withdraw their money from it).
The banks charge some fees that can be avoided by cutting them out of the transaction. Even small percentage-based fees add up to a lot of money on real estate sized transactions.
The seller is also the buyer of a different property and they or the other seller wants to transact in cash for one of the above reasons, so they would prefer to have cash from this transaction to use for the other one.
In theory the transaction could be made to involve the banks by everyone doing extra work for no reason, but at the margin that scuttles the transaction and even when it doesn't it still generates overhead that dampens the local economy makes peoples lives harder unnecessarily.