Besides I don't think the purpose of the save dialog is to list files as an actual filemanager would.
You might be surprised. Save dialog folder view widgets are often pretty full-featured (or just straight-up share code with file manager widgets), letting you do things like create new folders, rename existing files, and maybe even copy/paste.
In fact, I just moseyed over to my desktop to check: using the save dialog in Kate, I can right-click in the folder view and create new folders or files, rename files, trash files, and open files (in another Kate tab or in a different program entirely). It won't let me copy and paste, though, and drag-and-dropping a file from another folder into it navigates there and sets it up to overwrite it with the saved data, rather than moving or duplicating the file to the previously viewed location.

