SQLite can be used for many many applications.

Full-Text Search, JSON, high volume time serie data, Queue, Vector database, Cache (redis), file system (file under 100kB), graph database.

and again: the DB can fits in RAM or doesn't need a server. It's a simple file and avoid network requests for everything!

About some comparison:

For blobs under roughly 100KB, SQLite reads and writes faster than individual files on disk, and uses about 20% less space on top of it. The reason is that the file system charges you an open() and a close() and a directory traversal per item, while SQLite charges you one already-open file handle and a B-tree seek.
And here’s the kicker: a Redis GET over localhost is on the order of 100 microseconds. A SQLite point lookup against a warm page cache is on the order of 1 microsecond.