Lots of reasons for apathy.

Maybe its akin to what happens to hospital staff: the ones that care get destroyed by it, there is always more pain to deal with, while the ones that dull the feelings dont suffer from burn out so fast.

Our perceptions are no longer limited to what happens around us and what we are told by those we trust. Its hard to keep caring in a world that will show you every pain happening anywhere at any time, always. Many would rather dull that pain than go mad feeling it all.