We're not rational beings, so what do you do about an irrational fear? You invent a magical thing that protects from that irrational fear.
You're orders of magnitude more likely to die in a road accident, but people don't fear that. They fear terrorist attacks far more.
You can't protect against an opponent who's motivated to learn the inherent vulnerabilities of our systems, many of which can't be protected against due to the laws of physics and practicality - short of forcing everyone to travel naked and strapped in like cattle, with no luggage. And even then, what about the extremist who works for the airline?
So you invent some theater to stop people from panicking (a far more real danger). And that's a perfectly acceptable solution.