When you copy a shared column in a view and paste it in another view, it looses its "sharedness", i.e. converted into a normal column.
When creating big applications, where shared columns make the most sense, its normal to create variations of existing views. In this process, one would copy an existing view and add/remove some columns.
It would be easier and faster to open another view with the shared columns needed and to copy and paste them into the new view. But doing so, the column will be "disconnected" from the shared column. Thus you have to go through right click - insert or append shared column - search for the column in a possibly long list - insert - close dialog.