> Plus, if work vehicles became lighter, work trailers would be forced to as well.

Try shopping for utility trailers. Anything affordable is very heavy steel & lumber. You can get light(er) trailers in aluminum but the price is much higher. I've never actually seen a contractor with one of those, too expensive.

And of course there is all the materials & equipment they're towing on it for the job. How do you suggest any of that become lighter?