The worldwide population and the US population both have doubled since 1950, which incidentally is around the time that the television started becoming a (middle class) household appliance. 

While percentage drops, raw numbers still increase, the News broadcasts what will increase viewers, and the cycle begins. It's not that it's happening more frequently, it's just that there's more coverage of more events.

As I heard years ago:

"God's making more assholes everyday, but he ain't making anymore. land.