"t takes someone on the outside who has no idea how hard the job is to come along and undertake the task that conventional wisdom holds is impossible"
I've worked a little in both (software and class A driving) and I can tell you the outside perspectives can be a problem too. Really, self driving trucks on clear interstate highways are a few years off, but complete replacement in cities is a long way off. Its not about sensors that slam brakes on like a little Google car, its about facts like that at 40 tons, they take 7 seconds to come to stop, so you are contantly predicting human actions 15 seconds into the future and things like that.
Its a situation of diminishing returns to try for city driving as well. Trucking pays so well because long haul drivers are away from home for weeks at a time, and it's the mindless driving on major highways where pay costs stack up. But local drivers grabbing trailers from drones gets them home every night, so its way less hours paid and easy to hire the best. Also, the customer infrastructure isnt there for no human drop off and pickups. Even empty self driving trucks on highway would take major changes to DOT laws and infrastructure.