You can thank President Nixon and Executive Order 11615 in August of 1971 for the modern system of secret distributor discounts and inflated list prices.
Distribution multipliers were an obvious and simple way to circumvent price stabilization, and old habits die hard.
We get an example of that every time Boeing announces a big fleet agreement; "Four billion dollars worth of jetliners (at list prices) !" that actually sell for a fraction of that.