Good insight -- the incentives are on maximizing number of deliveries per unit time. I certainly hear (and sometime even see) UPS drivers gunning their giant diesel vans down my street only to hit a stop sign every block.

So the interesting question is can operating costs make their way into the incentive structure (theoretically it should be able to with good vehicle telemetry).

Whether it's worth it or not to adopt that incentive structure is another question: is the cost of fuel and maintenance greater or less than the marginal revenue from each additional package? Because you're right, currently the incentives are infamous for maximizing number of deliveries. However, the famous UPS-minimize-left-turns routing optimization story suggests operating costs do factor in as well.