Did anyone else expect that self-driving cars would be so much easier than natural language?

Not I -- they seem like different kinds of messy. Self-driving cars have to deal with the messy, unpredictable natural world, but within a fairly narrow set of constraints. Many very simple organisms can find their way along a course while avoiding obstacles and harm; driving obviously isn't trivial to automate, but it just seems orders of magnitude easier than automating a system that can effectively interface with the behavior-and-communication protocols of eusocial apes, as it were.