Many of these places don't allow workers to detain shoplifters, only specially trained "managers" and such....And sometimes they aren't in the vicinity or the theft happens on their days off....
In fact, many places will fire a worker who attempts to detain a shoplifter because it's against the store's policy....Reason is that it's dangerous and could lead to the worker being injured or killed....And if that happens....You guessed it!.....Family members will SUE SUE SUE the company....So, better to be safe and "non-negligent" by having a policy prohibiting such actions by workers....