Big old uncompressed texture files, much the same reason Titanfall and BF4 need masses of VRAM despite not looking particularly jaw dropping (although BF4 on ultra certainly has it's moments).Sigmund Av Volsung said:Even if they ask for 3GB of VRAM(why? I have no idea. It's still Frostbite 3, so it shouldn't hog that much at high settings).
With the new consoles having 8GB of RAM on tap (well 5) devs are getting a lot more lazy on how they use textures, when you consider what Crysis did with 512MB it becomes particularly obvious.