Thy mostly do that with their most popular first party titles. There are a lot of games that have never been released on other platforms. Some MGS series games

Thy mostly do that with their most popular first party titles. There are a lot of games that have never been released on other platforms. Some MGS series games have been released on one platform only and those platforms are no longer supported. If you want to play something like MGS: Twin Snakes legally you have to find a used copy somewhere (and hope that the discs haven't been damaged) and get the original console (and hope that the hardware isn't faulty) to either play the game on it or dump the game somehow. (Dumping might not be legal everywhere). Or you can just sail the high seas and play it on your PC. I doubt that anyone is going to port less known games to modern systems any time soon.