The lack of commercial availability is at least a small factor. It takes a fairly large tree to yield nice cue squares and persimmon is a very slow growing species. Some have used it here and there though.
It is a true ebony. I believe Dickie has told a story before describing how persimmon wood was once purchased from this country by asian purchasers (I forget who exactly) and then died black. After dying it black they were selling it back to the US as ebony, which technically was quite true. It takes a very large persimmon tree to yield a solid black turning square as the sap wood to black pith wood ratio is large.