Any software component that uses this standard would reference the XSD definition file, at run time, automatically (through third party library routines) to ensure that any messages it receives and any that it generates are valid and conformant with the standard. So the effort involved in developing such software can be concentrated on doing the really useful work and not diverted into developing the supporting infrastructure.
The Standard aims to achieve universal applicability by covering the broadest range of information while maintaining the efficiency and relevance of the content by declaring as many fields as possible as "optional" without breaking the underlying semantic model.