Getting caught is a failure. A bomb exploding is a victory.
There is a practically limitless supply of shmucks out there for AQ to weaponize. All they have to do is get better at converting them. What evidence do we have that this will be a long-term operational problem for AQ? Everything I see indicates that they will get better at it, not worse.
This is also why they aren't shutting down traffic lights. A failed attempt to shut down traffic lights wins nothing. Nobody is viscerally afraid of darkened traffic lights. In fact, until it happens, nobody is going to be viscerally afraid of someone taking out the grid. But everyone is afraid in their gut of exploding planes. Just the threat --- just 5% of the threat --- is enough to wreak havoc.