While not strictly illegal to not have a namespace in a schema, it ends up not being very usable for SOAP. As such the FUSE cxf-bc rejects such elements or at best tries to re-map them to the service namespace. Direct children of soap:body and soap:header must be namespace qualified per the soap spec. A "default" namespace is not allowed, thus, the schemas for those children must have a targetNamespace defined.
Also, the attribute elementFormDefault="qualified" indicates that there should be a namespace associated with the element in order to qualify the element.
SOAPUI may take a different approach to such nodes but this is the manner in which FUSE addresses them.
I hope this information is of help.