This document https://docs.openshift.com/container-platform/3.7/architecture/service_catalog/index.html  needs to be refined with a discussion about asynchronous operations.  

In 3.7 Service Instances could be provisioned, updated and deprovisioned asynchronously (in the backgound) if supported by the Service Broker.  Some operations may take a long time to complete (5-10 minutes or more).  Also, sometimes a Service Broker may be unavailable and Service Catalog will have to queue and retry an operation.  In these situations, end users may not be aware that the operation is still in progress and Service Catalog will continuously try to bring reality into accordance with the desired state.

When a user deletes a project that contains applications created by Service Catalog, it may take some time for the Catalog and the Broker to fully clean up.  Until these operations are done successfully the project and namespace can not be deleted.

Please see comment #5 in https://bugzilla.redhat.com/show_bug.cgi?id=1541350  for additional details.  

In 3.9 we add the async operations for Service Bindings (create/updated/delete).