[osmarks]

A filesystem is a hierarchical key-value database, which is not what many applications actually want, and plain text is not a data format for anything except structureless human-readable-only, well, plain text. While you could then put some textual format like JSON or ad-hoc space separated values or something into a text file, the tooling around text files may not deal with this very well. And it's slower than something like SQLite and lacks the aforementioned convenient syncing capabilities.