Why should you not create or modify items directly on the web database?

The rationale behind not creating or modifying items directly on the web database is primarily related to the nature of how Sitecore operates, particularly concerning item publishing. When changes are made directly to the web database, those modifications are not tracked or reflected in the master database, which is where the authoritative version of content resides. As a result, if content is changed in the web database, it is not persisted for future sessions, and any modifications will be unrecoverable after the next publish operation from the master to the web database occurs. Essentially, this means that the changes made directly to the web database are transient and can vanish unexpectedly, leading to data loss and inconsistency between the master and web databases.

This helps maintain the integrity and consistency of content, adhering to a structured content management routine that Sitecore promotes. Making changes only through the approved workflows ensures that all modifications are properly tracked, versioned, and published, preventing the kind of issues that can arise from direct changes to the web database.

While other options touch on valid concerns, they do not capture the primary reason as clearly as the issue of data persistence and consistency during publish operations.