In a practical sense, people DO have their own expectation of privacy in being "lost in the crowd" when in public places, regardless of what the legal systems project & rationalize.

Regarding public roads, we need licensing and insurance because we can severely damage other people sharing the same space, but that's not necessarily linked to consent to eliminate privacy there. We expect as reasonable for license plates to be recorded when something bad or suspicious happens, and that things like comprehensive license plate tracking is an invasion of privacy.