If you want locks from the same user you'd use other mechanisms that file locks. File locks are for processes that don't have a lighter weight way to cooperate. (e.g. semaphores.)
Also, there's a reason that databases have processes dedicated to writing (e.g. Postgres writer process, Oracle dbwr)
Don't forget that it still needs to synchronize across process boundaries, too - two processes, both running SQLite, and both accessing the same database file, is a supported scenario.
Also, there's a reason that databases have processes dedicated to writing (e.g. Postgres writer process, Oracle dbwr)
Fun fact - IBM's MVS didn't have file locks.