Well, different URLs are typically different resources; it wouldn't make sense for the search engine to index article?date=20040910 because article?date=20031001had some relevant keywords (ditto for article/2004/09/10 and article/2003/10/01) .
As to why a whole bunch of files is used instead of URL rewriting ... it's certainly nothing to do with search-engine optimisation because a search engine wouldn't care even if it knew.
I was going to make a facetious comment, but seeing as it was missed first time around (despite being flagged).... 🙂