I don't know how to respond to that. Some truths are just self-evident. You do what you want in your shower, and I'll do what I want in mine.
It was self evident to me until I analized the concept with an adult mind. "Civilized people don't do that" is not a reason for not doing a thing. It begs the question, "why not." If there is no answer, then my paradigm shifts and I do the thing, if consequences of doing it enhance my life.
So far they have. 8^>
Funny thing is, when I confessed it to my wife a year ago she said "I know you do." I asked how she knew and she said she can tell by the sound in the shower when I am. Her attitude is "why wouldn't you?" And she means women too!
That sounds a lot like, "it's just how I've been conditioned, but I've never actually stopped to wonder if it made sense."
Caesar: "Pardon him Theodotus: he is a barbarian, and thinks that the customs of his tribe and island are the laws of nature."
-- Caesar and Cleopatra, Act II, George Bernard Shaw
"That which is unchallenged and exercised as habit rapidly becomes ritual. When this occurs, dissent becomes an object of surprise, if not resentment."
-- B. Carmon Hardy