I'd think it's a legal strategy. By not prohibiting it, some scumbag lawyer can position that as a tacit endorsement of the individual's personal use of lethal force on their property. If a bystander is injured or killed, they'd potentially be liable. I can even see a scenario where the bad guy sued. I'm just guessing here, but I suspect their insurer requires it. Bottom line- I'm in a place that prohibits carry over a thousand times a year. And I don't care. The only way anyone is ever going to know is when there's gray matter splattered all over the cashier. And at that point the violation of some fragile little technicality most likey isn't going to matter.