I am pleased to hear from so many barbershop polecats. I am, somewhat, surprised that some of you differentiate between barbershop and folk. I don't care what your defination of folk is, barbershop, definitelt, qualifies. Of course, the repitore tends to be limited. So does every genre of traditional music. The songs are, indeed, American classics from the gilded age and the costumes, which are not unlike music hall garb, are comparable to such recreation mindsets as Morris dancing or historical reenactment.
The formality of the costuming harkens back to a time when performers understood that their appearence was an important aspect of their presentation.
There can be no doubt that, musically, barbershoppers live in the past and, if that doesn't qualify them as traditional, I don't know what does.