Why using the disc icon as saving icon is considered good
Regardless whether skeumorphism is good or not; a diskette icon for saving is passé.
But there is no better.
We could use a mobile phone as icon for saving as we use a mobile phone for that. And anything else.
We could have a mobile phone as icon for everything. It would be easier to remember just one icon. It would save band width as it could be cached. Support calls would be easier as we could just answer “press the button with the mobile phone icon”.
Diskette icon, CC0 license (http://creativecommons.org/publicdomain/zero/1.0/deed.en) (fromhttp://pixabay.com/en/floppy-disk-symbol-signs-symbols-24172/)