I know it seems odd, but there is a technical reason why it works that way. Let me explain, and forgive me for having to discuss gory details…
The Item Window is made up of data from different database tables. The description, pictures, eBay specific fields, Amazon specific fields, etc. all are in different tables for various reasons. When we open the item window, we create a new item. If you enter title text and exit before leaving the window, the item will be aborted. Once you enter at least a title and hit enter, we then create the Item from the base Items table. Since each item has a unique itemid, we have to create the item before we can link it to other tables.
At this point you can make changes to any many fields i.e. productid, prices, etc. and hitting Cancel will cancel those changes. If however at any time you add pictures or open the description editor, certain technical restrictions require us to save the item as it is first. So at that point anything entered on the item will be saved and no longer cancellable. Any changes made after the editing of description or picture can once again be cancelled.
I know it isn’t intuitive and shouldn’t work this way, but it is a very hard technical problem to solve based on the amount of information we have to link to in the Item window.