Because a "drought" is relative. In this context it also has a legal definition.
Or do you think the definition of "drought" is independent of expectations and demand? If there was not 10 million people in LA, a huge agriculture industry, and yes, lawns in suburbia, there would be plenty of water right now in California. Relatively plenty. And hence, there would be no drought.
So yes, lawns in suburbia have everything to do with a "naturally-occurring", but in reality created by human demand, drought.
