Yes, because Snap doesn't support different repositories easily and everything atm is based on Ubuntu base-images. Also the license is GPL+CLA allowing Canonical to relicense it under a proprietary license. Furthermore they require AppArmore for some features which some distros can't use (it isn't part of the mainline kernel AFAIK).

Fair enough. On the otherhand, does it really matter? The result is the same. GNUStep had Application Bundles and was developed in the 90s. ROX Filer had AppDirs and was developed in the late 90s and early aughties. Klik (now AppImage) was developed in the early aughties.

There's plenty of NIH to go around on this one.