National - Bay Area Airport Locations Closing Early?

I was trying to book rentals for OAK and SJC, and if I inputed anything for the pickup time past 11pm (most later-day east coast flights arrive at/after 11p), the website stated the location was closed.

Avis and Hertz are open either 24 hours, or until the last flight has arrived. Why is National closing so early?

OAK isn't a 24/7 airport for passengers. So, the "minor" car rental agencies don't have the vehicle demand to stay open late.