Comment by mostdataisnice

As someone replied above, it's because SQL is just 1 backend and it's weird to expose an API that only works on 1 backend. Once you have many devs working together, you need a remote server. If you have a remote abstracted backend, it needs to have a unified API surface so the same client can talk to any backend. You might argue "This interface should be SQL", and to that I would say there are many file stores (like your local file system) that are not easy to control with SQL.