That did make sense at the time, given that the Nokia chargers were as close as we got to a de-facto standard.
But yes, the move to USB has greatly simplified matters, in an as-confusing-as-possible sort of way.
None of these things are waterproof, of course. I'm not sure what the ideal solution to that is, other than enclosing things. Inductive charging is inefficient, which isn't what you want here. Something like the old Garmin serial connector would probably be how I'd attempt to make a waterproof charging port on a handheld device. Or swappable batteries a la eTrex, which is increasingly impractical for phones, just as 18650 cells have become sort-of mainstream.