Ok, you discovered my colloquial use of a technical word. I know most Californians live in what is technically a "Mediterranean" climate. But relevant to the topic at hand: most Californians get well under 20 inches of rain per year. It isn't a "desert" biome, but "Desert" at least gets you in the right mindset.
A cursory google search suggests that grass lawns need the equivalent of 1" of rain per week. Very few people live in the parts of California that get 50+ inches per year, which was the original point. Grass lawns are entirely unsuited to the parts of California where almost everyone lives.
https://upload.wikimedia.org/wikipedia/commons/6/6c/K%C3%B6p...