Originally Posted by
Pesky Monkey
Because you could never "attack" an aircraft while using a real boarding pass and real id.

But but but we have to prevent
Another 9/11™
You see, that was committed by 19 bad dudes with no criminal backgrounds who used real passports from their real country of origin containing their real name and photo to buy real airline tickets under their real name and then used their real boarding pass to fly while they followed all carry on regulations in place at the time.
These new ID regulations are designed to stop people like that from flying.