In a mostly driverless industry there will be protocols and standards a human driver will not be able to fulfill. Using humans in these workflows will be a nuisance.
Being able to 1.9x equipment utilization rates (or cut transit times over 21 hours) will guarantee adoption.
You see, they will be cheaper at first. Or maybe they don't even need to if demand outpaces supply. And then slowly companies begin to rely on them. And once the industry is completely destroyed, they will slowly up their margins. I know, unheard of.