Here's why:
* Reference sources are designed to provide information on a specific topic. They are not meant to be comprehensive or exhaustive, but rather to offer summaries and overviews.
* Databases are organized collections of data, typically in a structured format that allows for searching and retrieval. While encyclopedias contain a vast amount of data, they are not structured in the same way as a database.
While encyclopedias may use some database-like features (like indexes and internal links), their primary purpose is to provide easily accessible information on a range of topics, making them a valuable reference source.