Linux

The idea is you package the software once and it works forever, because all dependencies for it are provided in the exact right version. And the dependencies may include things that would not be included in the base system (like super new versions of some important libraries).

That is true, but that is also the problem: both the package and all its dependencies may be left never updated.

In traditional Linux distribution, like Debian, every package must be compiled within the same system, which usually means specific version of all key libraries. And when the key libraries are upgraded some packages compiled for older versions won't work, the package might not even compile with newer version of the libraries. And it is often not possible/practical to provide multiple different version of libraries (or other shared system components). The result is distribution developers have a lot of hard work updating all the packages. When there is no one to fix a package for the next version of the package, the package will be removed from the distribution. That happens when package is not maintained upstream and/or no one cares enough to maintain it in the distribution. In that case – is it worth to keep it?

Snap makes packaging applications much easier, and more decoupled from the operating system 'core'. Less maintenance is needed… but that also means less maintenance will be done, which is not necessarily good.

On the other hand, Snap allows application to be maintained more rapidly than the distro core – in that case it can make things safer – fix in applications and their dependencies can be fixed that it could be done in the normal Debian release process. But that depends on maintainers of the specific snap and its dependencies.