It's one a package contains it's dependencies, and often their dependencies too (transitive deps).'

packages are supposed to be nodes in a dependency graph (or better, partial order), and there are nice composition rules. But one the nodes themselves represent graph/order closures (or almost-closure) we use that nice property.

People that are very application oriented tend to like vendoring --- "my application is its own island, who gives a shit". But the distro's point isn't just gather the software --- that's an anachronism --- but plan a coherent whole. And applications who only care about themselves are terrible for that.

The larger point is free and open source software really should be library-first. Siloed Applicationns are a terrible UI and holdover from the economics of proprietary shrink-wrapped software which itself is a skeuomorphism from the physical world of nonreplicable goods.