The reason major businesses haven't bothered using distributed blockchains for auditing is because they fundamentally do not actually help in any way with auditing.

At the end of the day, the blockchain is just a ledger. At some point a person has to enter the information into that ledger.

Now, hear me out here, because this is going to be some totally out there craziness that is going to blow your mind... What happens if that person lies?

Like, you've built your huge, complicated system to track every banana you buy from the farm to the grocery store... But what happens if the shipper just sends you a different crate of bananas with the wrong label on them? How does your system solve that? What happens if the company growing your bananas claims to use only ethical practices but in reality their workers are effectively slaves? How does a blockchain help fix that?

The data in a system is only as good as your ability to verify it. Verifying the integrity of the data within systems was largely a solved problem long before distributed blockchains came along, and was rarely if ever the primary avenue for fraud. It's the human components of these systems where fraud can most easily occur. And distributed blockchains do absolutely nothing to solve that.