> I always liked how windows could have portable apps.

Linux has portable apps too - AppImages and static binaries.

As for Macs, dmg files are not apps, they're just archives like zip files. The apps go inside the dmg files. And these "apps" are actually just plain old folders with extra metadata that makes macOS treat it like it was an executable. But you can infact navigate to the inside of an app if you use the terminal, like you can literally `cd` to it and treat it like a folder that it is.