Here is my take on DW and external extractors.
I have a DW Panther, and the external extractor just works. Just about every other semi-auto under the sun has external extractors. There is no reason why an external extractor can't work on a 1911. But from what I understand, Sig, S&W, and Kimber all had problems at first with their external extractors. Sig and S&W fixed the problems, but Kimber had a fatal flaw in their extractor design (way too short) and instead of fixing it just ditched the external extractor and went with an internal extractor.
There are so many Kimbers made, when they screw something up (and their external extractors were a major cluster) it has major repercussions, and they gave external extractors a very bad reputation among 1911 aficionados, who tend to be conservative anyhow and don't like people tinkering with JMB's design.
Between the bad rap Kimber caused, and the 1911 purists who would not like an external extractor no matter how well it worked, trying to be competitive with an unpopular feature is an uphill battle. Sig and S&W are 800 pound gorillas than can pretty much do what they want, and they obviously decided not to cater to the purists with their 1911s. I guess when CZ took over DW, they decided to go the more traditional route.
