Having lived through the 70s, part of the issue was the amount of media coverage hijackings received.

The Entebbe raid was the canonical example, playing out as it did over a full week: https://en.wikipedia.org/wiki/Entebbe_raid

And there had been another hijacking just the week before that one.

You can quote statistics at people all you want, but when something like a plane hijacking is happening nearly two out of every three months on average (throughout the entire 1970s), and sometimes on a weekly basis, and making a big splash in the media every time, people are going to want something to change.