Even though I get your point and I am convinced you're using "simple" aptly, I will nitpick the obvious: passive headphones can be deceptively simple or a marvel of engineering.
If you didn't get the chance to listen to some music through proper audiophile headphones, I do recommend to spend some time at the closest audio retailer and live the experience.
From the many people I have asked this question, I think the disconnect between toilet phone users and us is the availability of "Alone time".
Specifically no matter what you do in your house/work for some there is always low key chance of someone bothering you. This is not the case when you appear to be using the toilet.
One port, singular -- there's not enough knee real estate for multiple devices.
Open the laundry chute, it's in there along with a Thinkpad brick, both wired up from the basement. Ends have magnets that captivate them to the chute door for safe keeping.
A joke about "ports" or "drops" in the bathroom is trying to form itself in my mind, but I am actively suppressing it to protect myself and the community.
most phone support USB-C to ethernet. Always remember their are weirdos out there who are so into mobile games they have docked phones attached to cooling systems.
Same reason I don't use WiFi at home but ethernet: it's simple.