News stories are often recycled.  Shortened versions of the original may run again during other newscasts.  Also, with the popularity of video over the internet, television stations now have more staying power than ever through their websites.  You will notice that the same news stories aired during the evening newscasts are being placed on news station websites and can remain there for several days, if not months.  Also, television newscasts create buzz in a local community.  For those viewers who are often too busy to catch the live evening newscast, they will choose to log onto a news station's website at a later time to catch up on what they missed.