That would be nice if companies simply relinquished the reins of control to the users after they decided to stop supporting or selling their products, but they don't often have this sensiblity.
If that were the case, abandonware would no longer be a grey area in the realm of internet morals, our general knowledge of programming and software would be truly vast indeed...
However, companies also want to make a profit. Just because it's old never meant it was bad. But, if you keep using the old software without procuring new software, then they run the risk of loosing potential customers. Furthermore, turning all that hard-learned knowledge over to the masses means that, now, potential competitors can capitalize on that data, jump-starting their own products which might pose a risk to the income of the company that formerly released the data. Even if you can't legally sell derivatives of the original work, that won't stop you from reverse-engineering the work, and then implementing the desired features into your own. Who would know?
Now, that gets rediculous with products that are going on 20 years old, and it's likely that some of the companies don't exist any more and that their source data is gone forever. But why does Lucas Arts and EA hold on to the rights of archaic games still? Well, granted, now they realize that they can still make a profit by selling them over the net from recent years, which I'm fine with so long as their practices are reasonable. But, meh, we could rant on ethics and rationale for hours. The point is a company seldom does anything that could be construed as not in their interest. Giving up information means that someone else can use it, and that means it might be a loss to you.
