Subuser is not a revolutionary peice of software. You are right that it is a LOT like a zip file or tar.gz file full of bundled dependencies. It is, however, a big improvement on just that. Subuser contains the subusers, so they cannot mess with the rest of your system, making a lot eisier to trust those bundled dependencies. It also provides some rather primitive update mechanisms for those bundled dependencies. But it's main advantage is the containment and the "blank slate".

In the future, I would like to expand on the vision, to include the ability to do deduplication, so that all those zip files with bundled dependencies take up less space. And deduplication done right, will save bandwidth too. Indeed, when you have these "deduplicated zip files", with deduplication done algorithmically, you'll save even MORE space and MORE bandwidth than with a traditional dependency resolving file manager. Take for example debian. Debian uses packages. These packages have dependencies. The dependencies are shared. This saves space over a case where you have a bunch of zip files with unshared dependencies. But when you update a dependency, even if only one line of one file has changed, that dependency must be downloaded completely anew. But with algorithmic de-duplication, updating one line of one file means you only have to download one line of one file anew.

Space savings are there for a similar reason.