The Freakonomics guys love to talk about how humans are terrible at assessing risks.
Why do we feel safe in the middle of cars moving at lethal speeds and nothing but symbolic paint lines to keep them from plowing into your face?
Why do we use social media so liberally?
Why do we eat basically anything someone else gives to us?
I guess when I think about it, we probably just don't want the stress that paranoia brings. Anything we could gain from being ultra-paranoid is probably outweighed by the happiness lost by living in fear.
We may be terrible at assessing risks, but I think it's better to be good at letting ourselves be happy.