Hands-on with PostgreSQL Authorization
While it's controversial to put business logic in your database, I suspect it is not controversial to claim that it's important to understand the permissions and security of your database. If you neglect learning how your database handles authorization, then you probably aren't following the principle of least privilege — your database might be accessed by coworkers (e.g. developers, data scientists, marketers, accountants), contractors, continuous integration processes, or deployed services that have more privileges than they should, which increases the risk of data leaks, improper data access (e.g. of personal identifiable information), and accidental or malicious data corruption and data loss.
Source: Hands-on with PostgreSQL Authorization - Part 1 - Roles and Grants, an article by Greg Schafer.