There seems to be some confusion about the difference between historical music and traditional music. Studying the past to determine musical style and instrumentation isn't traditional -- it's academic musicology, which in some ways is the exact opposite of traditional. I play music with origins that range over a 700 year period; if I were to only use the instruments that were current when each song first came into existence, I'd have to drive around with a large truck full of instruments.
There also seems to be confusion over the fact that our wonderful English language allows us to use the same words for different meanings depending on context. The "traditional" in traditional song, to me, refers to the provenance of the song, not the milieu or style in which it is sung. Communities have traditions. These traditions root the community to the past but are also constantly changing. When traditional songs first came into being in their traditional communities, they were modern music and were played on whatever instrument came to hand. In today's society, playing traditional music on the electric guitar could be argued to be more traditional than playing it on a concertina or hurdy-gurdy . . .
If you are going to exclude electric guitars from traditional music, you may as well also exclude acoustic guitars, accordions, flutes with keys, violins, etc. How far back do you want to go to establish what is traditional and what isn't?