I am pretty sure you are underestimating how important it is for them. But we can look at their own scientific publications.[1]

No maps no driving....carnival ride...

"High Definition (HD) maps are maps with precise definitions of road lanes with rich semantics of the traffic rules. They are critical for several key stages in an autonomous driving system, including motion forecasting and planning. However, there are only a small amount of real-world road topologies and geometries, which significantly limits our ability to test out the self-driving stack to generalize onto new unseen scenarios..."

[1] - https://waymo.com/research/hdmapgen-a-hierarchical-graph-gen...