“Purpose built” is simply defined by Merriam-Webster as “built for a particular purpose.”
A paring knife is purpose built with a short-curved blade specifically to pare fruit. You probably could use it to cut a loaf of bread, but why would you when you can have a bread knife purpose built for that loaf?
There are a lot of purpose-built trucks out there, often referred to as work trucks. Utilities use bucket trucks to access powerlines. Waste haulers use garbage trucks. E-commerce deliveries use box trucks. Each of these has been optimized for their specific vocation.
Class 8 tractors are the Swiss Army knife of trucks. Designed to pull a trailer, they mostly don’t care what that trailer is — a dry van, refrigerated van, 28’, 45’ 48’, 53’, flat bed, drop, tanker, bulk carrier, car carrier, soft side, container chassis, dump, livestock, pole, you name it — if it has a king pin, odds are a Class 8 tractor can probably pull it.
Pulling it efficiently, now that’s a different story all together.
The industry has been trending towards specialization for first owner duty cycle for a long time. Fuel efficient aerodynamic tractors really took off in the 1990s. A combination of market and regulatory forces has continuously optimized this segment through today. These aerodynamic tractors have optimized powertrains for on-highway pulling dry and refrigerated van trailers, themselves also often equipped with aerodynamic treatments.
These highway flyers are less well optimized for second, third and fourth buyers. Yes, they can probably pull most any trailer, but they are not as well suited for those other duty cycles.
