Running `find /System/Library/ -name "*.pdf"` reveals that macOS uses many .pdf files as icons or UI elements. For example, the VPN connection animation in the menu bar seems to cycle through a sequence of .pdf files located at:<p>/System/Library/CoreServices/Menu Extras/VPN.menu/Contents/Resources/VPN[0-4].pdf<p>Why PDF, instead of more traditional formats like PNG or SVG? Is this due to Quartz/CoreGraphics rendering benefits, vector scaling efficiency, or something else?