If you absolutely need a way to install dependencies globally such that they can be shared between apps, you can still do that without version conflicts if you write proper manifests for them and use https://en.wikipedia.org/wiki/Side-by-side_assembly.
But it's easier to just package a local copy and not worry about any of this, so that's what people mostly do now.
But it's easier to just package a local copy and not worry about any of this, so that's what people mostly do now.