The English guitar actually originated in Germany, it was known in France as guittare allemande. The cittern is also, originally, from the continent. The modern cittern, bouzouki, mandola and octave mandolin family have no direct connection to the renaissance cittern or English guitar, rather they are developments of the Greek bouzouki (which has it's origins in the Arabic oud)or the mandolin and differ from each other only in scale length and the number of strings, the cittern having 10 and the others usually 8. You might as well ask why folk singers don't wear doublet and hose in my opinion.