Let's see if you think it's a security theatre next time you fly from Jordan to Israel. Or actually anywhere within the US, where gun carry is allowed...

Sopmer of it is theatre but screening people to make sure they don't have a bomb ios not theatre - people will do this as has been shown.

It is a bit weird in that screening started only after bombing... a useful metric would be to see how many times bookings/hijackings were thwarted. (which I would guess many)

No screening started after hijacking in the 1970s.