I really hate to defend the TSA but there is a legitimate infiltration vector that this does address - that employees beyond the checkpoint can being in substances and transfer them to passengers
The simple solution is to put the employees through the same process as the passengers. Everyone who enters the area gets the same security treatment, even the head of Airport Security.
This is much simpler than randomly accosting passengers in the departure lounge. Wouldn't it be safer to not disturb the passengers even further?
I struck an annoyance similar to this in Manila Airport. Once we were through the security checks, scanning, frisking, etc we were herded into a roped off area only after again having our baggage and ourselves scanned and frisked, etc. This was because we were going to Australia, apparently.
Jet travel is stressful enough without these extra annoyances. Make a secure area and scan everyone who passes in through the barrier once only. It would be nice to wear lace-up shoes again while travelling by air