At some point media organizations found that people would rather watch a train wreck than the launch of a new high speed rail.
http://www.essex.ac.uk/government/epop/papers/panel7/p7_soro... - Concludes there is a psychophysiological evidence that negative news is more arousing.
I suppose it follows that media concerning terrorism is probably more arousing than people being crushed by couches, and makes much better TV. And our perception of our reality is heavily influenced by what we are exposed to.
A great example of this would be the coverage of the fertilizer plant that blew up in Texas verses the Boston marathon bombings. These happened within days of each other. Which one did you hear about more? Which one killed more people?