Every public bathroom is a mess. Urine on seats and the floor. But I've never gone to someone's house and seen their bathroom in that condition.
People act badly when no one is watching and they have reason to believe their badness won't be discovered.
I'm skeptical of the value of anonymity to the collective where it's obvious to see the value to the individual
I broadly agree with your premise, but the nitpicky HN part of my brain feels obligated to point out that a certain amount of selection bias might be at play here. Public bathrooms are by definition places the entire spectrum of the public visits, and is probably a broader and slightly more diverse pool than the people whose homes you personally visit (unless you're a social worker, which you probably aren't because then you would absolutely have seen swathes of homes that a lot of people here would probably deem uninhabitable)
That said, you're not wrong : we've all witnessed friends, acquaintances et al behave differently from one context to another. I live in Norway, and the prototypical example that comes to mind is that kids / young adults here are significantly more belligerent and antisocial abroad than at home where they are subject to the Scandinavian brand of tut-tut judgyness. Basically the spring break phenomenon so it's not unique by any means.
Not exactly, but close enough.
Why would people want to do that, even if nobody is watching, that's the question we need to be asking ourselves.