Hi – great question!
We haven’t made a conscious decision not to support it, it’s simply that it has not yet been implemented (and currently I don’t believe we have any concrete plans to do so). You can of course use the WordPress exporter (XML format) and could potentially transform this to another format like CSV by running it through a suitable application or script.
We’re always open to new feature requests, though, so do feel free to post a new one or add your support/comments to a suitable existing request (such as this one – though it’s not specific in terms of the output format).
Thanks!