Except high density displays are not really that common outside smartphones and the Apple world. It's probably safe to say most people still work on regular 1080p monitors at 90-100 dpi or at best on 1440p with slightly higher dpi. So an SVG with design resolution of 512×512 will look like a blurry mess when scaled down to 16×16. We'll get there eventually but optimising for low-density displays is still a very valid and reasonable thing to consider.