[Merovius]

And in regards to

> if these costs are being borne evenly, then it's complete societal waste.

that is exactly what is happening. Advertising is the classical real world example for the prisoners dilemma. It is literally the reason, why game theory exists. Every company can chose to advertise (defect) or not advertise (cooperate). If no one advertises, everyone is better off. But that is not a stable equilibrium, so instead everyone is advertising, even though it incurs some cost on social wellfare.