Why exactly is Homeland Security acting as if it still would be possible to hijack an American airline with box cutters?

Yes, we all know that the horrific 911 attacks were perpetrated by terrorists armed merely with box cutters, which have small enough blades that they don't easily trigger metal detectors. However, we must really bear in mind the fact that the events of 911 were a direct consequence of the psychology of terrorists up to that point in time, which had not been suicidal. It was assumed that terrorists did actually want to survive the results of the terror they inflicted, and, hence, that accommodating them was the best strategy for hostages, if they also wanted to survive. What made the catastrophic damage of 911 possible was this simple fact. If the airline passengers had realized exactly what their captors had in mind, of course, they would simply have attacked and overwhelmed them, the twin towers wouldn't have gone down, and, although some of the airplanes might have gone down, the overall damage done would have been much, much less. If anyone tried to hijack an American airline with box cutters these days, they'd be beaten to death by the passengers. Indeed, if anyone tried to hijack an American airline these days with an AK-47, they'd be beaten to death by the passengers! Nevertheless, really the entire 50 billion dollar annual security expenditure on DHS is based on the assumption that nothing has changed since 911. The entire mass groping phenomenon by security at American airlines is the direct consequence of the assumption that terrorists armed with box cutters could do the same kind of damage now that they did on 911, and, this is patently ridiculous. One can quite readily imagine a time in the not too distant future when all those DHS gropers at American airports will be charged with sexual assault -- remember, no statute of limitations on sexual assault now -- just like lots of doctors are now being charged with sexual assault for what they probably thought were just routine physical exams. These DHS gropers might want to bear this in mind! All it takes is enough ladies going to their district attorneys' offices or filing lawsuits to change the entire attitude to this behavior! Indeed the entire security DHS culture in the U.S. really is quite questionable. Do we really need Real ID? Do we really need all the security around top secret inaccessible facilities for producing driver's licenses and IDs, all the expense and inconvenience of these obstacles to simply obtaining proper identification? Are terrorists still going to be able to crash into skyscrapers because of our simple desire to accommodate them, like the experts told us to do? Are we, as usual, fighting the last battle, rather than the next one?