"collectors tend to buy "names" and the "names" in photography for all of the 19th century and most of the 20th centuries were b&w photographers."
and related to that ... old usually means more valuable. old and dead usually means much more valuable. color photography's only been around for a few decades as a serious art medium; digital versions less than that. it will be a while before there are a competitive number of names, and then old names, and then dead names. but you can be sure the collectors are waiting.