I have a 1912 house but the main useage bathroom on the second floor is a total remodel. Not a great one, but a remodel. There is a hole with a built-in (well, two drywall screws worth built-in) bookcase behind it, covering all the pertinent plumbing parts for the tub/shower.

Just after we moved in I needed some kind of service to the first floor bathroom toilet. Plumber accidentally broke that intake pipe. However it was just in the basement and had direct access. He installed new pipe and a new turn-off valve, it wasn't as costly because all the crap is accessible. But that bathroom,.. we need to redo the tub plumbing and that will take pulling off paneling in a stairwell. yikes.