The thefts keep happening because they put one overworked nerd in charge of six lanes at once, seven if they have to open the register at their little podium because the store is running on a skeleton crew again and the only other lane is being run by a poky senior citizen who can barely walk. The minute literally anything goes wrong the ONE nerd has to turn their back to everything else and walk the customer through fixing it while reassuring them that they're not going to be clapped in irons for accidentally scanning something twice, so everyone else just wanders away with their bags of chips.