The airlines pre 9/11 went along with it because it cut down on sales of throw away returns. I remember certain LA classified papers back in the 90's that had pages and pages of ads for tickets to NY for anywhere from $10-100, it was a convenient way to make back money on tickets that you were going to throw away.

As I recall, EVERY SINGLE ONE of the 9/11 hijackers was carrying ther own ID, the fault lay in not grabbing the 2 of them that had something on ther records. The ID thing is a pallative to make idiots feel more secure. Most European governments have had strict/mandatory ID regimes for decades, yet neither airline checks or anyother sort have done much to catch any terrorists, either because they are using their own names and are not on the radar or using real ID's with fake details, which are not on the radar.