The shared quarters seen in The Undiscovered Country were horrible. Did not jive with all the fabulous stuff we are expected to believe the future holds. Someone missed the psyche memo about personal space.
I think there must be public toilets on each deck, crew can't be going back to their quarters for every wee. As to the bathing.. I am going to assume that 7 gets cleaned while regenerating. A build up of dirt or grease is inefficient, if they are having their gears cleaned the rest of them is probably cleaned too in the regeneration alcove.
This is all just to torture us, we will NEVER SEE 7 IN THE BATH.
Thankfully we get to see Janeway taking inefficient baths. And uhh.. Neelix.