Given that I would like the bilge pump to keep working as long as it can (even if thoroughly beaten.... I plan to ensure waterproof connectivity at least to the top of the engine compartment. I was just wondering why this is not normal practice (at least on my boat).
I don't think exposed circuits in the bilge is normal practice in the marine industry. I certainly have not seen it. Having said that, I have seen factory installations, boat yard work and DIY projects that just made me wonder Why, Why, Why?
For example; a friends power boat has factory installed through hulls with sea cocks beneath the engines. It is tough enough for a small person to access the valves on a calm day, dockside, while the engines are cool. For a larger person (like me), in big seas, with hot engines, in an emergency situation, it simply is not going to happen. Good practice would dictate closing these valves when the boat was unattended. However, I'd be willing to bet most of the owners don't even know the valves are there! Several more practical locations exist for the valves, but I have to assume the choice was made for the convenience of construction at the factory. I see this in cars all the time, however in this situation, it's certainly a safety issue.
Point being, even if the bus bar mentioned in the OP was installed at the factory (or by a PO), it don't necessarily make it right!