App bundles don't use resource forks, but they do often use extended attributes and aliases and things. Although it's possible to make a zip file with those thi

App bundles don't use resource forks, but they do often use extended attributes and aliases and things. Although it's possible to make a zip file with those things, not every zip program does it by default. But mostly I think it's just tradition, and maybe some small secondary features like being able to show a EULA when someone double-clicks the disk image.