It won't be just "one" driver, it would more of them, as in the lorries are usually stopped where other lorries are also stopped (at lorry-specific parking spots, for example) and as such it would be harder for the robbers to confront an "united" (for lack of a better word) pack of drivers. Granted, robberies (and even murders [1]) still happen in those circumstances, too, but give the robbers unattended merchandise sitting by the roadside and then see what will happen.

[1] https://www.digi24.ro/stiri/externe/mapamond/au-fost-arestat...

That's more for the driver's own safety, as the burglars could have lethal weapons.

If it were autonomous it could defend itself and its contents without risk to humans. At the very least with fart spray, pepper spray, itch powder, and the like.