A question for truckers and mechanics

ok, a corvette with 400 bhp is going to be producing it at something like 5000 rpm and getting pretty poor gas mileage. It has tall gearing to enable it to achieve high speeds and only has to shift 1.5 tons of car.
Big diesels in trucks tend to be around 12-15 litres, and whilst "only" producing 425 bhp for example, they will do it at 12-1300 RPM, as you say for long periods of time. its all to do with operating economy. a 14 litre truck engine pulling 30 tons could still potentially get 8+ mpg and last a million miles, whereas if you drive your corvette using every one of its available BHP all the time its not going to last long and will drink gas like crazy. horses for courses. The bhp vs torque is a trade off to get the most power whilst retaining economy and longevity- basically the smallest amount to do the job.
Once you have reached a HP rating whereby the truck can pull a full load up a steep hill without having to downshift excessively and still return good MPG there is no point going any higher. It will never be a performance machine due to the tiny power band, low gearing and sheer number of gears.(anywhere between 8 and 18 these days). Big diesels are sloggers, with large capacities to make them unstressed to last the distnace.

Because they don't need stupendous amounts of horsepower to move down the road. It's the torque that does it. Your average semi puts down roughly 1400 to nearly 2000 foot pounds of torque.