I agree. However, I believe the reason for this is more legislative laziness than anything else.

In the wake of a terrorist attack, the public demands that laws be changed to make them safer. The executive's law enforcement and intelligence agencies typically have a wish list that they repeatedly ask the legislature to enact, because it would make their jobs easier. The legislature, under tremendous pressure to do anything and fast, does not attempt to really analyze the legislation, but rather uses every parliamentary trick to rush it through.

The executive uses these expanded powers to check off national security goals it already had in mind (see e.g. the hundreds of arrests during the French state of emergency.)

The end result is threefold:

First the executive is emboldened to at least look like they're increasing security at home and abroad. At its worst, it either draws the nation into a war on territory chosen by the terrorists (see e.g. Afghanistan, the rock upon which the Soviet military machine shattered), or needless wars of choice which drain economic and military effectiveness (see e.g. Iraq)

Second, the country experiences an economic shock far out proportion to the actual attack, due to the fear of the populace, which directly and indirectly depresses multiple sectors of the economy.

Third, the country produces highly visible, although not necessarily highly effective, responses at the expense of sacrifice of civil liberties and personal convenience.

What's more is that terrorists count on this reaction.

They know that the costs of the response will vastly outweigh the actual damage of the attack.These particular non-state actors are deemed "terrorists" for a reason. Because their most powerful weapons are not airliners, or bombs, or assault rifles.

Their most powerful weapon is fear.

They use that fear to cause nations to make poor decisions, then exploit those decisions to advance their causes. The only solution which I can devise is simply not let fear arbitrate our decisions.

We must announce, as one voice, that we are no longer afraid.