Lots has been written about this.

The post-9/11 freakout is a GREAT example of the syllogism "Something must be done! This is something, so we must do it!" -- IOW, a train of thought that includes absolutely no evaluation of efficacy.

Security expert Bruce Schneier noted, I believe, that the only things that came out of the post-9/11 freakout that mattered were (a) the reinforced cockpit door and (b) ensuring all the checked bags go with an actual passenger.

The ID requirement, for example, was a giveaway to the airlines to prevent folks from selling frequent-flier tickets (which was absolutely a common thing back then). (And wouldn't have mattered on 9/11 anyway, since all the hijackers had valid ID.)