Fuel pumps inside automotive fuel tanks, which operate submerged in the liquid, frequently have electrical contacts that are completely exposed to the liquid (or vapors, if the fuel level in the tank is low enough)!
Yeah, it's only 12 volts, but 12 volts DC can still make a pretty good spark.
Reason 1: Can't ignite when in a submerged liquid. and the air space above the fuel is either too rich to ignite (gasoline engine) or too lean to ignite (diesel fuel).
Reason 2: It's pretty inaccessible, and not prone to getting a foreign object short-circuiting the terminals.