Trucking is also one of the largest sources of employment in the country. It's quite literally the backbone not just because they haul so much, but because they are a massive source of income for families.
I'm not saying trucks are bad or that we should get rid of them or that truckers shouldn't be paid or anything like that. If we closed the externality of trucking causing more damage than they pay for then trucking and transportation would get better. The trucking companies would have more information to make decisions about what routes/equipment/etc are worthwhile.