There are more reasons then committing a crime for wanting anonymity. If I was someone with money like a celebrity I would want this phone. If I was a business with sensitive information I would want this phone. And so on.
They quickly found their primary market was, well... crime.
I think this part is underestimated by most people. Celebrities are frequently under a microscope and having to live your life while worrying about somebody overhearing it and taking it to the press must be frustrating. Everyone has bad moments in their lives, but at least for most of us these won't be dragged up and published to the world. A device like this could help alleviate that fear a little bit.