WAV, you answered your own point in your post of 18/6 05:42 pm referring to seeing it in a 17th century reenactment on TV.

Most people in the folk revival are trying to continue a tradition that was and is alive (albeit much reduced) in the 20th and 21st centuries. We use instruments appropriate to this period.

The English guitar/cittern is appropriate for 17 century reenactments but its not appropriate now. There was a brief fad for early music instruments in the 1960s and 70s but it rightly dropped out of fashion.