Of course not, and no one ever said that. But if applied correctly they make coins lose your taint (note: taint in the neutral sense of tracked coins, not in a criminal sense). And that's the one you want to get rid of.

Tumblers and coinjoins are important for both fungibility and privacy because they make the concept of taint pretty much useless. And you want the concept of taint to be pretty much useless, because otherwise you couldn't accept Bitcoin payments for fear of receiving tainted coins -- even if coins would look untainted to you, they could still look tainted to someone else. And a currency you can't accept is a currency you can't spend is a useless currency.

@All: Sorry for having derailed the thread, I hope you enjoy the show.