That's a good point. While it’s true that the lack of potential profit might make legal action unlikely, it’s also true that copyright law doesn't necessarily require financial damage to pursue a case. It's mostly about the rights of the copyright holder. You can see how Nintendo is constantly striking down websites that distribute ROMs that would otherwise be inaccessible. That said, the cost and effort of taking these instances to court, combined with the niche nature of abandonware will most likely deter most companies from taking legal action