If you got poop on any other part of your body, would wiping it with some dry paper convince you that you were clean?

That is... an unexpectedly good argument.

Not a great argument for people who wash other parts of their body with soap, hot water, and scrubbing with a cloth.

Yeah, water alone does not a clean surface make. Mythbusters showed this in their "air dryer vs. paper towls" myth.

Water plus soap = clean hands no matter the drying method. Water alone, and the paper towels did better than an air dry.

Wait, would you only squirt it with water?

Nah, I didn't say that either.

so what is the alternative?

You rinse off thoroughly with water, airdry/drip for a few seconds, and then dry/scrub with a smaller piece of TP.

If you ask a typical parent with an infant, dry paper isn't quite enough, but wet-wipes are; they're just more expensive and not flushable.

You'd also use soap elsewhere.

Absent soap, I'd rather use paper than just water. I'd bet it's strictly more hygienic too. Moving water spreads stuff everywhere.

Maybe, but it seems in practice that either option is fine hygiene-wise - there surely would be definitive proof one way or the other by now, given widespread use, of there were issues?

There's a paper about parachutes and problems with proving they prevent death that seems applicable here.

Not really relevant, given that a huge fraction of the world uses bidets. Unless you're implying that a huge portion of the world is eschewing parachutes and apparently doin' OK.

This was my realization as well.

This is my question as well.