There are several reasons why a search engine prioritizes search requests over indexing, including the potential for every search to be a game-changer and the importance of relevance. To achieve maximum speed and relevance, a search engine must balance fast updates with wide applicability, and indexing best practices can help ensure this balance. The most important indexing practice is batching, which involves updating multiple records in one indexing operation, and other best practices include sending only changed attributes and performing incremental updates to reduce indexing request sizes. By following these best practices, a search engine can optimize its indexing speed and relevance for any use case.