While it would be nice to believe that search engines solve the issue automagically, there are a lot of reasons why organizations want to reduce they amount of old/outdated/stale information that's served to searchers. I know where I work, we're constantly deleting older material (at least for certain types of content--which news and quasi-news pubs doesn't necessarily fall into).
What reasons would there to be to delete old new articles? My inner historian is screaming.
There are infrastructure costs and manage costs.