1. Data in a database is generally subject to CRUD operations. Blockchains are Immutable (unalterable). Modifying records in a Blockchain defeats its purpose. Modifying records in a replicated database is required.
2. Blockchain is called a distributed ledger because a ledger cannot be altered. An accountant in a business cannot just alter records in the company ledger, as its illegal. Blockchain is the same way, except records cannot be altered because of reliance on the consensus algorithm, that is, SHA-256.