I would think that the caps would help not only with water, but also dust. Then, consider where you live, maybe near the ocean, and they throw in maybe damp salt laden air...corrosion could be costly and enough dust accumulation could make inserting the plug impossible or add to any wear. Having lived in the US southwest, I know a dust storm gets dust everywhere...doesn't matter if the flap is closed. Then, throw in maybe a sprinkle, or a car wash, and that dust can turn to almost rock. I do not know if there is any voltage on those pins - it's likely they only get connected via a contactor, but if you have the DC fast charge port, who knows. There's probably a diode in there to prevent that. If BMW didn't feel they were necessary, they wouldn't put them on the vehicle, IMHO.
