Over the ages, people have cunningly hidden secret documents inside other items - paintings, boxes, trees, that sort of thing. It's been a common theme in spy thrillers, too.
Most people have documents that they consider to be secret.
Whether they're actually of any interest or relevance to other people is sometimes questionable, but there are very good reasons to keep business and financial information private. One of the two main components of Steganos is its encryption engine. Using an almost inconceivably high 2048-bit level encryption, it would be very hard indeed to determine the contents of a file once it had been encrypted using Steganos. But if you encrypt something, you invite curiosity. Anyone discovering an encrypted file will wonder what it contains.