Warloch_Ahead: Probably because of lost source code.
You don't need the source code to put out a game digitally.
Shmacky-McNuts: Silent Hill 4, is not a Silent Hill game at all. Seriously. It has nothing to do with the series, because it was a totally different project. Which is why it is the only one on gog. The publisher considers it to be worthless. As it is.
Silent Hill 4 was always supposed to be part of the franchise despite the BS fake rumor that it wasn't. I get it, you hate it because it's not the same old tired formula, but that doesn't mean that it wasn't meant to be a Silent Hill.