Transparency:
Since a blockchain is a distributed ledger that is stored on a network, everyone has access to the same data, which cannot be edited without the consensus of a network that is financially incentivized to remain honest.
Security:
As opposed to centralized databases, a blockchain is immutable and data can only be added to the ledger via a consensus mechanism where nodes are financially incentivized to be honest. This eliminates the risk of unilateral data tampering.
Improved traceability:
Blockchain is a high-availability public ledger, which means that all transactions can be tracked by anyone at any time and the provenance of goods can be verified to ensure authenticity and prevent fraud. This is in contrast to traditional supply chains, where relevant data can be cluttered, inaccessible and mutable.
Increased efficiency and speed:
Traditional databases are often paper-heavy and prone to human error. Also there is the problem of redundancy - data about a particular event is often stored by multiple parties in different ledgers that need to be reconciled, which is costly. Using a single ledger streamlines this process.
Reduced cost:
Since the blockchain is trustless, it eliminates costs associated with outsourcing trust, i.e. using middlemen like banks, insurance companies, etc.