In many cases, bans can have unintended side effects which might make the means of acquiring/distributing/producing "banned X" far worse (aka the cure is worse than the disease).

At least in the case of South Korea, all porn is treated equally illegally, so the country has a really high incidence of secret cameras peeping in places like women’s bathrooms, because that’s just as illegal as a scripted porn film.

You're the only one who asserted a percentage. So allow me to clarify, when I wrote that comment I had no belief that a law need be 100% effective for it to be a useful law. I also believe there's a lot of room between 100% effective and "backfiring". I don't believe this is a binary situation but there's a spectrum (that isn't one dimensional)

I hope with this added context that my previous comment will make much more sense and you can interpret it closer to what I intended.

I'll just add, I don't think most people work in those absolutes. So I'd be wary of jumping to the extreme interpretation. People might interpret you as being disingenuous and using the logical fallacy "logical extreme" or "reductio ad absurdum". But I'm pretty sure you're not doing that because then I'd be grossly misinterpreting you, right?