When most of you Spring xml config files are not in your classpath or in your war file, but directly in your file system on a computer.
But really even if you use any of the XmlApplicationContexts, the type is just the default loading mechanism, and you can always overwrite that with the prefixes.
http:
classpath:
file:
I actually recommend always using the prefixes on all resource loading, xml config files, .properties file loading etc.