Technical limitations in older consoles likely led to the separation of save points and checkpoints.

I think the answer is for technical reasons rather than design reasons. God of War was designed for the PlayStation 2 and Resident Evil 4 originally appeared on the GameCube (and later on PlayStation 2 and Wii). These consoles take a few seconds to write a save to the memory card, so doing this every time the designers wanted a checkpoint would probably have been too annoying to the player.