Interoperability is exactly the reason why control characters weren't added to xml 1.0.

And

>You are encouraged to create or generate XML 1.0 documents if you do not need the new features in XML 1.1; XML Parsers are expected to understand both XML 1.0 and XML 1.1.

XML 1.1 was considered a failure by W3C and it is not recommended that anybody use it.