You seem determined to take issue with the concept of a bidet. That’s OK no one is forcing you to use one. The toilet seat attachment ones are super cheap and convenient. You don’t have to get up and go anywhere. You just turn a knob when you’re done pooping and you get cleaner than you can with paper. Feels good to be clean.

Like back to the arm poop analogy, if you for some reason were getting shit on your arm every single day, sometimes multiple times, then having to go do the shower soap towell thing becomes a hassle. Maybe it makes sense to have a special hose next to where you keep getting shit on you to make clean up easier.

It’s a single wipe on clean skin. Much less paper used. No abraison. No mess. If you got shit on your arm would you be satisfied just wiping if off with paper?

I’m pretty sure the muscles are controlled by the same nerves/neural pathways. A lot of people can’t shit without pissing also but once you have shat you don’t need to hold those muscles so you can let loose. It’s a bit like trying to wiggle your ring finger without moving your pinky or middle. Except with your dick.