In the Irish tradition there are many waltzes with words that many people dance to. Obviously you havent a clue.

Apparently I haven't. I've not come across any of these sung waltzes myself, but I'll take your word for it. However, based on the observation that the number of singers working the folk dance circuit here is precisely zero, my conclusion is that in the UK the demand for folk dances is for bands.

Of course, singers may also play in bands, and may even sing songs for some dances. This has to be done sparingly, because the tradition here is to have someone to call the dances, which can't be done while someone is singing.

My point is that at most festivals most of the performers are singers, not dance band musicians. The market for singers is a different one. Performing at festivals won't generate a lot of "private" work for them (unless you include folk clubs in this category).