It's not they shouldn't be listed.
They are listed because they are possible upgrade paths to products you already own.
it may be that you have an older version of dreamweaver for working on older projects and in that version of dreamweaver you would like to upgrade to UE4.
There are possible scenarios where you as the customer may want to purchase the UE4 upgrade and the Data Bridge Upgrade. for the majority, that wont be the case, but it is up to you.