I'm a 60 year old male and have watched it ever since the first show, when I was on holiday on the Isle of Lewis. Never been much interested in dance before, but did watch Come Dancing occasionally years ago. That was boring, all that formation stuff. This show is much more "happening".
I think it's the combination of professionals and well known people of differing abilities going outside their comfort zone that makes it interesting and all ages tend to watch it, although I suppose the majority are over 40 and mostly women. Nonetheless, it is quite cool for blokes to like it without being labelled a cissy.