A few things off of the top of my head.

1) The increase in technological innovation means we have access to more data ie more bad stories even if the overall amount of 'events' are falling, thus giving the illusion that violence is on the increase.
This is the 'fault' of the media but in an unconscious sense.

2) As children we were less aware of 'problems' around us; this is true for children today, and one day they will look back at a seemingly benign early 21st century.

3)Much more insidious, in what can only be said to be my personal opinion, is the conscious racking up of fear by some sections of the media for political and social reasons.
The differences in progressive and conservative mindsets are played out in politics, economics and social attitudes. As one gets older it is more difficult to be come accustomed to change - most change is for the better, though where it is not surely evidence based reasoning should point to where corrections need to be made.
Conservatives(small c) think all progress is detrimental, for reasons I pointed out above, and want the world to stop and stay the same. I read a scientific study recently that tested levels of disgust, and conservatives had a much lower level of disgust tolerance. They are also the section of the population that are most fearful about aspects of life. Papers like the Daily Mail play on this fear as a way to control the political and social agenda - they actually deliberately wrench up the fear in the population as a matter of editorial policy.
Conservatives also crave order; in the sense that someone, be it a supernatural governor of all life etc or an ultimate all wise authority leading their society is in charge; that there is stability, change frightens them as it breaks through the notion of an accepted order...the fact is that reality is actually in constant flux, no one is in charge.....therefore they cling to what they know from their past....it's always better no matter what the evidence suggests. To be fair the majority of humans subscribe to this notion completely unaware of it, not just conservatives. This trait of humanity can be easily harnessed by other to control politics and society and some media deliberately use this as a tactic

Just a vague snapshot of my thoughts - I could go on but really I have better things to do :P