Why does loki backend depend on gateway?

I am trying to set up a Loki cluster as. Simple Scalable. From the configuration in the Quick start ( Quickstart to run Loki locally | Grafana Loki documentation ) page, the backend needs to depend on gateway. The dependency is read,write <= gateway <= backend.

If I put “condition: service_healthy” for all the dependencies of gateway and backend, then read will start as unhealthy because backend is not started. I can accept that gateway doesn’t need to wait for healthiness of read and write before it starts, but I just want to know why backend depends on gateway.