I once sent the same question to Support back in Qlikview 9.00.7119 AJAX.
--> Support answered back then that this is a WAD (working as designed) (Casenumber 00011323)
It looks like qliktech have been unable to create the same "copy to clipboard" functionality in Ajax as they have in the standard app or the ie-plugin. Probably due to limitations in what can be achieved in browser only technology. Hopefully some of the new capabilities available in HTML5 will enable them to resolve this.
Note that if the user right clicks and hits print it will actually create a new window with the chart object as an image in it. They can then right click -> save image as. Not perfect but might be good enough.
In Ajax if you have also turned on the special icon "Copy Image To Clipbaord" this also changes to a "Print" button.