I’ve refused to buy Domino’s Pizzas for several years for just this reason...
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.