We have some "parent/composite" items that have a number of child items.
When the parent item goes out of stock, we have to manually check each
child item individually to see the stock levels and find out which of
the child items has gone out of stock.
If the current stock level of each child item was displayed on the composition tab of the parent item, we could see straight away which one was out of stock.
It's only a small issue, but one of those minor annoyances when it does happen.