Why No Bathrooms in Star Trek?

The opening of Star Trek promises that man "will boldly go where no man has gone before," but why does no one ever use a bathroom in any of the series? I've seen them all, and I've never seen anyone go to the bathroom, or say they had to take a break, or talked to a colleague while they combed their hair in the restroom mirror. They still must have bladders in the 24th century, right? Especially since genetic modification was considered a terrible idea that was tried and then rejected? Even all the other species must take a pee sometime, especially the Klingons, with all that drinking. But I don't remember anyone even mentioning it, even as humor, like the kind of humor they often used on Enterprise. I recall Troi or Riker splashing water on their face from one of those retracting sinks, and one episode opening with Captain Archer in the shower as the artificial gravity cut out, but no one ever does any business. Would that have ruined the certain sense of utopia that Gene Roddenberry tried to convey? Would it have required unsightly zippers in those one-piece uniforms? How do you pee in one of those, anyway? Especially 7 of 9.

And if Vulcans have green blood, what color is their pee?