I believe it is the combination of
a) desensitisation due to being overloaded by media all these years of all sorts of atrocities.
b) the realisation that we can't really do anything to change it.
Yes I could join some rallies and what not to show my disgust at what is going on in the world, but if I truly believe it won't do anything, am I not only doing it for show?
I don't think that you should ignore the issue - but when I find out what I can do to actually help, im sure I'll act upon it.