Thanks for all the comments and good wishes.
This was already a big topic and is expanding all the time.
It seems to me that there is somrthing here about performance contexts and the relationship with competitions. My experience of Irish dancing is that the competition is the context ie, very little happens outside of the competition scene for most dancers, whereas with Irish music, hundreds of musicians compete, but there is also a vibrant session scene, both at a fleadh itself, but also more generally. The same with rapper dancing. Although DERT (Dancing England Rapper Tournament) may be a focus, there are plenty of other opportunities for performing rapper in other contexts.
Does this fit with other experiences, such as those mentioned in the thread, i.e. Eisteddfodau, or Northumberland piping?