I still remember when my parents first bought the house in which I spent most of my childhood and teen years, and us finding a full bathroom in the basement, with a concrete shower stall. I remember everyone joking about it, wondering who the heck would ever want to use a concrete shower in the basement, with two other shower stalls and a tub in the bathrooms upstairs.
Then it came time to was our lab-shepherd mix, and dad suddenly realized the brilliance of the prior owner... who also had dogs. Thereafter, that became the dog's shower.