I commend your critical thinking process. In regards to supply chain, the purpose for blockchain to replace a database is simply irrevocable data. You can't alter blockchain whereas you can always fudge a number or two in a database. Can't keep track of missing shipments of expensive handbags etc. So in regards to supply chain, it's a great idea and a great example of blockchain in the real world.
It also means you are storing every state of every thing in the supply chain. There is one transaction for it leaving the warehouse (status = "in transit") and another record for it being delivered (status = "delivered"). That could be a silly amount of data compared to setting a flag, in a record, in a database.