"The market decides."

Precisely. For any act - WHATEVER THE GENRE - to successfully break into a less specialist and more mainstream audience, it will almost inevitably have be 'dumbed down' to a degree and made safe for consumers who expect a certain ease of listening. Just look at how ordinary sounding Lady Gaga is, once you get past the theatrical garb, her brand of pleasant and not very challenging danceable pop has been doing the rounds for something like twenty years now. That's the world of top of the pops for you.

In order to appeal to the mass market, It's highly unlikely that more rootsy type folk acts of the kind which might appeal to those of a strongly traditional bent, is ever going to make it big. The Unthanks seem like a very pretty and pleasant sounding folk act, and while their brand of music is not particularly interesting to me, I certainly do not begrudge them success among more mainstream audiences.