I think a lot of it is a kind of learned desensitization. The constant bombardment of advertising from a young age, and 24-hour news cycles conditions a natural response of cynicism and numbness to certain kinds of alarming messages. Our brains are already saturated with the kind of "buy this and you'll be happy" and "the world is scary and falling apart" messages that we develop categorical methods of dealing with all messages of that form. It is a painful act to care about something and be let down later, and it is painful to care about things that you feel like you can't do anything about. Add in a generally accepted (if thinly veiled) terrorism narrative and a socially acceptable practice of "let's not talk about politics" and you get the kind of response you've been getting.