We trust the TSOs (and to a lesser extent, the airport employees) after a single background check.

Until they get the magic one-time very limited background check, TSOs are just ordinary members of the population. Once they have passed that simple little check, they are trusted for life as long as they are in uniform Why is it that a similar process won't work for ordinary members of the population?

It's not like a TSO has never 'gone bad' after passing a background check. If the argument against 'trusted traveller' is that a background check is no guarantee of future trustworthiness, then we should be screening everyone, including TSOs, all the time, every time they enter the sterile area.

If a single background check is deemed to reduce the odds enough to take a risk, then ordinary flyers should be able to get one and avoid the checkpoint crap just as easily as TSOs.