Ya, I wonder the same thing. In an extreme case it seems like you could build dedicated repeaters/cell phone towers/something along specific stretches of highway, and then start testing along just that stretch with remote operators on call. I suspect remote operators are cheaper than devoted drivers, potentially making a profit from that transition alone, and also collect training data to develop full autonomy.
You need at least a minute to get into the context and have full situational awareness, to imagine what it would be like as a remote driver with less lead time than that, think about a scenario where you suddenly wake up with your hands on the wheel, with no idea where you are and no idea what's going on, except the situation is probably bad.
Any kind of remote assistance will most likely not include steering the truck in real time over the internet.
Rather, things like "unknown obstacle on the road, can't continue", with the operator instructing it to just run over that empty cardboard box. All realtime safety decision-making should have safe autonomous fallbacks, a human cannot be expected to drop in and take charge in seconds. The entire level 3 / 4 "semiautomation" market is a bunch of make believe.
Cell networks are even longer lead time and more capital intensive than autonomous driving ;) even if we only consider the fcc + local permitting time, it already makes this option difficult.
