California has the second highest total lane miles by state[0] and it has the highest number of registered vehicles of any state, by a big margin.[1]

Being a such a populous big state with only tiny, regional public transportation systems means everyone and their cousin drives everywhere, all the time. That's how.

[0]https://blog.cubitplanning.com/2010/02/road-miles-by-state/

[1]https://www.bts.gov/browse-statistical-products-and-data/sta...