I used to think this sort of thing too. Then a few years ago I worked with a SWE who had experience in the trucking industry. His take was that most trucking companies are too small scale to benefit from this. The median trucking operation is basically run by the owner's wife in a notebook or spreadsheet- and so their ability to get the benefits of leader/follower mileage like that just doesn't exist. He thought that maybe the very largest operators- Walmart and Amazon- could benefit from this, but he thought that no one else could.

This was why he went into industrial robotics instead, where it was clear that the finances could work out today.