One point of clarification (or correction, not quite sure) - using GraphQL as an API Gateway (as opposed to the GraphQL server directly talking to the data layer) for 1st-party clients is actually pretty common in the GraphQL world.
What's less common is using the GraphQL server for service-to-service communication, though i've been aware of people using it this way for my entire 3 years with GraphQL. I'm not yet convinced it's superior to alternative solutions to this problem (like gRPC, Thrift, other API Gateway patterns like JSON-API), but it could well be. I'm still happy using GraphQL in its sweet spot (and not-coincidentally what it was designed for), which is building an API for 1st-party websites and apps.
What's less common is using the GraphQL server for service-to-service communication, though i've been aware of people using it this way for my entire 3 years with GraphQL. I'm not yet convinced it's superior to alternative solutions to this problem (like gRPC, Thrift, other API Gateway patterns like JSON-API), but it could well be. I'm still happy using GraphQL in its sweet spot (and not-coincidentally what it was designed for), which is building an API for 1st-party websites and apps.