By controlling the means of distribution of the software (adopting an economic principle of scarcity,) the company that is producing the closed source product can profit from it. They promote security through obscurity. But eventually, as has been demonstrated in the past, someone, somewhere will figure it out: Consider the DVD's encryption scheme, which was broken in less than a year, by an open source movement programmer. As such, the companies would attempt to keep quiet many security risks to their system (as it devalues the product's and company's credibility.)