What some people might not realize is that those glass walls are there for the specific purpose of allowing passengers to keep an eye on their belongings. There is also the concern that if we took passengers into a closed-off area to screen them, we could abuse our power and "violate" them. In theory, allowing everyone to watch us screen the passengers keeps us above-board and honest.

Now, blocking off view of the entrance (and exit from the rear) of the checkpoint is a good idea. That way, the only look a person will get of the screening is during the limited period where they themselves are passing through it.