(As as side-note, it's of interest that arcade and home video game console ROMs, from roughly the same era, don't seem to fall into the abandonware class.. at least not so far as I have seen. Is this because the copyright holders are most often large, visible corporations? Perhaps, but it's also clear that the rights to a number of canonical abandonware titles, such as the Lucas Arts "SCUMM" point-and-click series, are likewise held by extant corporate concerns..)
It's because the authors of the old games can keep reselling the same stuff every time a new platform comes out. Windows versions, mobile phone versions, etc. Or at least the corporations that own the titles do.
There are still issues with ownership though. -- Ethan O'Toole