Nonsense, Kaleea. You're being too restrictive. People use tunes for all kinds of things, dancing being only one of them. Just as a tune for singing will often (usually?) deviate from danceability, so might a tune for its own sake. In Irish music at least, the listening qualities- which might include speed, emphasis, rhythm, and decoration amongst other things- might make that particular incarnation of the tune difficult or impossible to dance to.

Perhaps this is why Irish music players of an earlier generation used to refer to English music as "humpty-humpty".