In Short

Because water dissolves and carries away. Paper rubs and spreads.

What We've Been Sold as Normal

Paper is treated as a sufficient, final fix. A few wipes are supposed to remove residue. Cleanliness is defined by dryness. Friction is ignored or accepted as necessary.

The Honest Explanation

Excretions cling. Water loosens that grip, washes around the skin, and carries residue away. Paper can't do that. It only picks up what's already loose and pushes the rest across the surface. That creates friction. Friction irritates the skin, especially where it meets the mucous membrane. This is a mechanical effect, not a judgment about hygiene.

What You Often Hear – and What's True

"Paper is more hygienic."
Paper leaves more residue behind.

"Water just spreads everything around."
With enough flow, water carries it away.

"Wiping is faster."
Speed is no substitute for complete removal.

"That's just how it's done."
Habit is no proof of effectiveness.

Putting It in Context

Water cleans because it's physically suited to the job. Paper is a makeshift fix that became the norm.