Reason I think that is because a lot of features in ps3 cpu were not standard at the time plus this article says it would be hard to port this game to modern platforms: https://news.instant-gaming.com/en/articles/16364-konami-believes-that-remastering-metal-gear-solid-4-would-prove-very-difficult
I said I think because I do not know how much assembly the game uses all I know is it is a big amount because with linux part of it is written in assembly so it can use the nonstandard parts of the cpu and the cpu features of the ps3 were not standard at the time.