Litestream author here. I wrote an embedded key/value database called BoltDB a while back and I experimented with using it for application development. It had its pros and cons. The pros were that it was crazy fast and a lot of data access is just basic iterators. Some of the biggest cons were having to implement indexes on my own and that my schema was tied to my application language. Migrations can be more difficult if everything is tied to structs in your app and it's also difficult to inspect your database since there's no CLI REPL.
So the answer to my question might be "because SQLite already does some stuff really well, like indexes and its CLI, and it just happens to be relational and use SQL as its query language, but that's not the important part". I buy that.
