[drdaeman]

Yes, you're right. I've mentioned that technology in the comment above. ;)

Docker is just a quick-and-dirty way to have a full system image. It's somewhat simpler than building a proper .deb (.rpm, .tar.xz, whatever one distro eats) package, especially when there's a ton of dependencies from other packaging systems (PyPI, Ruby gems, npm packages, etc.)

Oh, and unlike with many popular OS packaging systems, with Docker can actually have multiple versions of the same "package" "installed" at the same time (that's my biggest issue with dpkg), but IIRC there are no built-in provision for the migration scripts (prerm, postinst - this sort of stuff).