First iteration of Google's APIs were atom. I do miss XML.
One of the API providers I use at work returns responses in XML and we use an XML parser to parse it to JSON and even then it's not perfect. What do you like about XML? I feel like I'm missing something.
Obviously, that's only a benefit if you care about and utilize those features; most teams doing JSON integrations will just build those into the consumer in lieu of them being provided by the transport. But it is something that some people (especially larger enterprise organizations) value.