I'm pretty sure they do, but I'm assuming people have learned ways to get around them like blind spots where they can just slowly pocket shit. It's pretty clear whatever they have in place doesn't work as intended for their anti theft/security. I bet you this guy had been squirreling away cards every shift for months or even a year before he finally tried to move them all. It's honestly really fucked, because had the guy been smart and slowly sold the cards he would have probably never been caught. There's certainly more than just this one guy doing it too, so who knows how much shit has been stolen off the line.