This can be frustrating at an airport like EWR. When there is a long line at security, there may be lanes avaliable for your bags to go on the belt but there pre-screnners are holiding up the line checking boarding passes.
A few years back at certain airports you had numerous people checking your boarding
pass. I am not sure what the obsession is with a boarding pass as if you don't have a valid one this means you are not getting an a airplane so you are no risk to anyone.