Not so much "can't" achieve it, but doesn't.<p>With xmlrpclib, serving functions over XML-RPC is a library import, a server class instantiation and a one line instruction to serve a function, and on the client side an import, a connection and a function call.<p>After that they behave much as any other functions (+latency), parameters are encoded and return values decoded all behind the scenes, neither the server function nor the client need have any special 'written-for-XML-RPC' changes for it to work.<p>It's more a case of a well implemented Python module than an inherent win over REST - there could be a similar module for REST-RPC created, but AFAIK there isn't one at the moment.