instead of non-relational, think of it as denormalized. I also can't think of any cases where you wouldn't want some relationships. I can absolutely rattle off tons of cases where applications benefit greatly from some kind of denormalization.
In years past, people called these "data warehouses" and essentially took snapshots of their production DBs and denormalized the hell out of them so that aggregations wouldn't crash the server.
In years past, people called these "data warehouses" and essentially took snapshots of their production DBs and denormalized the hell out of them so that aggregations wouldn't crash the server.