I'm not sure what you mean. While they don't call it "new" ballroom, people in ballroom dance to modern popular songs all the time. Same thing with swing. There are certainly venues that only play period music, but in my area it's not uncommon at all to throw in some current rock music. Moves are invented (or reinvented) all the time. As far as labels go, perhaps it is just because there is a strong traditionalist movement in tango. Music evolves. Dance evolves. Art evolves.