A lot of apps still use legacy Windows APIs that don't understand very long paths. Those APIs have been deprecated for maybe 15 years or more, but developers are lazy. Microsoft can't add support for long paths to the old APIs because they use a fixed buffer size (which means that only a certain amount of memory space is available for the path, and increasing it would break the apps that rely on that). They can't totally remove the old APIs because every app that uses them would break.