In a decentralized network, consensus is achieved through financial incentives. By creating a network of trustless verification, users can depend on the validity of the network without having to trust any individual party. This provides a situation where it is practically impossible to cheat and parties can rely on accurate and verified data.
In a central database the data is verified by individuals only through proof of authority and does not require consensus to be accepted into the ledger. The records can be changed or corrupted by the controlling entity or individuals without the need for verification from other parties involved. Trust of individual parties is required when working in a central database and the risk of fraud is high.