The way a company like a retailer delivers goods is an implementation detail under their control, not dictated purely by consumer habits. If the cost structure of shipping by truck changed, retailers would do a better job of traffic optimization or would even work out new operational processes that used fewer trucks. I know first-have that the current system has some real slack even at large retail chains.

Example: a lot of companies are not doing a great job of planning multi-hop truck routes and instead send a less full truck to every location. Similarly, the trucks are only full in one direction because that's easier to manage than planning routes that, for example, drop off at a store then visit a vendor before returning to a distribution center.

If trucking costs increased in proportion to road wear, you can bet improving these operational processes will be a higher priority!