Using XML is one of XMPP its biggest strengths. XML is well designed, good documented and has a rich set of supporting libraries. XML documents can be composed of other XML documents in a sound fashion, which is a major feature for an extensible protocol as XMPP is, and XML documents compress well, making them suitable in low-bandwidth conditions (see [XEP-0365](https://xmpp.org/extensions/xep-0365.html)). I also never experienced a considerable battery drain when autark devices are using XMPP compared to a binary protocol.