Let's use common resolution logic here. So, if you were to say... Viewing a video with 1200 quality and what not, it would be great. But with 240 quality it would be insanely shitty, and really blurry. It's still the same thing with the textures. Every picture has a resolution, the higher the quantity, the better. Also what Nuthug said, if you were to try inserting a 512 texture into a thing that was originally 128, it would look bad, really huge and insanely blurry. I can't tell if I explained it right, but I believe I did.