For Contact List and Drop-down list columns currently the values need to be added and updated individually in all columns and sheets eventhough the values are common for many columns and sheets.
If we have a provision to have the values referred using a reference from a different sheet, then we can add or update the values in the reference sheet. So that change will reflect to all Contact List and Drop-down list columns that have the value references. This will reduce the effort of updating the values individually in each and every Contact List and Drop-down list columns.