Most crosswalks in the US are not marked, and in all places I’m familiar with vehicles must stop or yield to pedestrians at unmarked crosswalks.

At unmarked crosswalks and marked but uncontrolled crosswalks we have to handle the situation with social cues about which direction the pedestrian wants to cross the street/road/highway and if they will feel safer crossing the road after a vehicle has passed than before (almost always for homeless pedestrians and frequently for pedestrians in moderate traffic).

If waymo can’t figure out if something intends or is likely to enter the highway they can’t drive a car. Those can be people at crosswalks, people crossing at places other than crosswalks, blind pedestrians crossing anywhere, deaf and blind pedestrians crossing even at controlled intersections, kids or wildlife or livestock running toward the road, etc.