I'd answer with:
Because it's a privacy nightmare.
They'll answer with:
I don't care about privacy,
I've got nothing to hide.
I'll answer with:
That's a dumb reply,
my privacy is not important,
but systematic privacy is,
if we don't care about it,
we'll end up in a oppressed surveillance state like China.
And then they say "huh" and likely will continue to not care.. ;-;
However it does make some aware,
in which I'm putting my faith.