 Why do web frameworks always use database?
yu: Taking 'information heavy' to mean large data size/ volume. File system can be seen as a basic database.  When data access paths are not pre-defined e.g. URL, slug, tag, etc., a systematic way to organize and query is required.  Three examples: (a) not knowing what user may query, text indexing today almost index every words.  (b) given predefined access path, NNTP have used mostly files.  (c) mail servers have both.  IMO, in general, addressing domain specific requirements, database systems (relational, logical, network...) are not slower, harder to update/ backup.  As pointed out in another comment, disk IO is slow.  Both file and database systems feature various ways to speed that.  Understanding requirements, then architect, design, and choose a solution stack carefully.