They haven't always had to. Presently, they do. Eventually, in a better world, they won't. Walking hasn't changed for millennia, and it won't in the foreseeable future. Riding in automobiles, however, is about to change completely.

Projecting our typical pissed-off aggressive auto-commuter attitudes into the future is a mistake, and will come to be seen as a sort of mental illness. Well-adjusted robocar passengers will pay no attention to traffic, just as normal people today don't constantly bother air stewardesses about how long their flight is taking.