Answer:
Probably a mix of all these mechanisms:
1) awareness - you are not aware of the problem all the time (what eyes can't see)
2) empathy - info you get doesn't move you; you haven't lived through the problem, so you know it "intellectually" (but do not feel it).
3) knowing what to do to solve the problem - usually there are no "direct" actions you can take to solve the problem
4) thinking that you can make a difference - usually you don't believe you can change such a big problem (AAAND it seems to be a lot of work ... probably for nothing).
5) thinking there are "govs and organisations" better suited to solve such problems.