Why bombing Royal Navy fuel storage was difficult

Why did Germany not concentrate on bombing British naval fuel storage during World War II?

Royal Navy fuel depots were difficult targets because important stores were protected in underground bunkers and even built into mountainsides.

Important Royal Navy fuel reserves were protected in large underground bunkers, including storage built into mountainsides. These depots were harder bombing targets than London. Officers and men could be housed in surface barracks nearby, with slit trenches for protection. The arrangement gave the fuel substantial shelter while leaving accommodation much more exposed.