And one technical / business side that's very valid: error-proofing the service and database. It is to prevent the database to be populated incorrectly, such as

And one technical / business side that's very valid: error-proofing the service and database. It is to prevent the database to be populated incorrectly, such as financial data, that you proof it behind a set of well-defined API, to prevent any leakage of sensitive data (PII or credit-card info) and to be easily audited.