Blake wrote a nice page on the benefits of using transactional-based enqueuing here:

https://riverqueue.com/docs/transactional-enqueueing

It's true that it's not distributed, but there are a lot of benefits to not going distributed immediately, like extremely predictable data consistency. I would hazard to guess that the _vast_ majority of apps that are not built by the superscalers are already using a database like Postgres or SQLite to store their data, and River merely suggests that you hook your job queue into the database that you already have.