Have you seen a container ship lately? MUCH of the cargo is carried well above the main deck, and there is little (if any) access to much of it. Also, I doubt individual containers have fire detection or suppression, so a fire would be detected only after a container was fully involved.
Fire mains and crew are fine in the engine room, but would be ineffective in the stack of containers above the main deck. They would also likely be of marginal effectiveness below the main deck.
I think it is significant that there are VERY few instances of electronics simply catching fire, even if you include the rash of bad laptop batteries a few years ago. I really believe there is something in the [lack of] packing and/or the quality of the batteries involved...