Why would you want a text-based query language if you are an idiomatic C# programmer? Every database product on that platform is queried through the standard LINQ syntax - that's why we implemented it that way.
* Interactive REPL (think psql)
* Use outside of C#, e.g. small bash scripts for automation of small tasks such as deleting old records in a cron job
* Copy/paste a into Slack, Github issues etc. without having to drag along any dependent code or worrying that it's not a complete query
Query builders are nice, but eventually they have to compile down to something "neutral" and portable.