What is this drop in value due to?
Quite simply, the keywords in a domain name hardly count for search engine rankings anymore. Where a few years ago keywords (in both domain name and in the HTML (code of a website) were still highly valued, there has been a change. After all, you could (for relatively high indexing) very easily put a large number of keywords in your code and choose a domain name, while the content of your website could contain very different content. And what does a search engine like Google benefit from? That a web searcher gets the information most relevant to him after a search, in other words quality content.
The introduction of Google's Panda (a sort of filter to exclude low-quality content from search results), led to a drop in the value of keywords related to SEO and actually more focus on serving the searcher well. After all, websites that continue to provide solid content remain on the safe side of the filter.