I'm no friend of trucks, but I wanted to clarify that 80,000 is the typical maximum weight allowed for a semi-truck. That would more likely be a shorter-haul truck moving gravel or other materials instead of less dense cargo like Walmart products. For the long-haul, materials are transported by train.
I'm a friend of trucks -- pretty much everything you have ever bought made its first and last trips by truck. There's no way modern logistics are feasible -- i.e. you don't get to buy stuff -- without trucks.
The weight being carried is a function of the number of axles on the truck. Each axle is good for about 8 tons, so your 80,000 pound load (40 (short) tons) is a 22 wheel tractor-trailer. You do need to balance the weight properly given the location of the axles, but this isn't rocket science.
There is a good reason for having a generally applied and precise limit on weight per axle: the wear and tear on the road is empirically proportional to the weight per axle to the fourth power. Those overloaded trucks or improperly loaded trucks do a lot of damage to the road, much more than you could ever do with a passenger car.