In transformers you see at power substations they use one of the following; mineral oil, SF6 (sulfur hexafluoride), or a complete vacuum along with nitrogen to reduce moisture. They do this to extinguish the arc that is created when the contacts are either made or broken. The SF6 is a great dielectric; however it has the same cooling properties as air, as would a complete vacuum. Not to mention that in a vacuum it would bear to get air flow.
Originally Posted by chechenepiphany
Plus you can't really use or sell any of the parts again unless you somehow manage to wash them without frying them.
When PCB's are made flux is in the solder, if this flux is not removed, i.e. washing, it will eventually break down the solder. You can get electronics wet, as long as they are not energized until they have had a very good amount of time to dry.