Look at it from the other side. Even with the lax security before, about 999,999,999,999 per billion people were deterred. That is a stupendously high success rate. We cannot make spacecraft with that high a quality level.

> If it takes a day of preparation, we'd see perhaps a dozen per day.

Nope. People are deterred by socialization and innate biology. I could take a gasoline bomb to a nearby school or church and kill hundreds of people within the week, for little expense and a good chance of getting off scot free. So could most people. It is not difficulty or risk that prevent mass killings.