I doubt any of the other pizza delivery places allow their employees to be armed either. The general rule of thumb in the often robbed industries (convenience stores, fastfood, taxis, home delivery) is unarmed and don’t fight back. The companies are afraid of getting sued but customers caught in the cross fire, they figure as long as all the bullets come from bad guys they’re safe from litigation.
It may be their policy but it isn't mine AND I STILL WON'T PATRONIZE DOMINOS' PIZZA. I still think their policy of disarming their delivery drivers and then sending them into places that police often won't go to in less than platoon strength and with kevlar helmets, armour and automatic weapons has cost drivers their lives!
Frequently these are college students working part time to help with the cost of getting an education (and with most of the Liberal College campii declaring themselves Gun Free Zones, these delivery drivers/students are already taking their lives in their hands just going to class).
Tell me who else does that and I'll add them to my list of places I won't do business with.