Because manufacturers don't typically have their own fulfillment infrastructure for retail-sized orders? What you're proposing with somebody buying a bulk orde

Because manufacturers don't typically have their own fulfillment infrastructure for retail-sized orders? What you're proposing with somebody buying a bulk order and divvying it up is basically describing what the existing retailers do. The reputable ones are worrying about their reputations. Retailers that aren't big enough to do this themselves go through suppliers, who in turn handle breaking a bulk order down into units to sell to smaller retailers. Those suppliers are worried about their reputations too, you just don't see that because you largely don't see them. (Edited to clarify)