I can already imagine the first comment that will show up here: “Nautilus already does this, so there’s no need to support it in GNOME Shell.”
But the Dash is an important part of the GNOME Shell experience, and it would be great if it could expose a few simple features. In the same way that we have Quick Settings for convenience, the Dash could also provide quick access to things like Trash and mounted volumes.
Yes, Nautilus already includes these features, but that is not really the point. If we followed that logic strictly, then Quick Settings would not exist either, since GNOME Control Center already handles those system configurations. The real value here is quick access.
Not every user wants to pin Nautilus to the Dash just to reach these functions. At the same time, this does not mean the Dash should become overly complex. The goal is to make better use of what is already there while still keeping the simplicity that GNOME Shell is known for.
Well if you are dash to dock user well it is the same exact thing.