Cecil Sharp's description of the dulcimer

I was recently looking through Cecil Sharp's works: "English Folk Songs from the Southern Appalachians" and stumbled upon several excerpts regarding the dulcimer. He states that he only saw the instrument in some of the Kentucky mountain schools and is only rarely found in homes. While I think that we can all agree that these books are a valuable resource, it is known that Sharp drew some wrong conclusions in his works regarding the nature of the songs and the mountain folk themselves. I was just wondering if any of you knew why he believed the dulcimer so rare when it clearly existed prominently in the states he visited.