I understand everybody's frustration with not being able to do this from the "it is my right to do this" point of view - with regard to deleting apps and app updates for this deleted apps. But please hear me out with regard to the Purchase History.
What most people fail to realize is that these records are tied into Apple's accounting system and no accounting system/software will allow you to remove a customer's purchase records from the system. If that was possible, accounting records could be inaccurate or falsified and their sales records would be a mess. As big as they are - I think even Apple must report income to the Federal Government. The bottom line is that you are asking Apple to remove those sales transactions from their records when you ask if you can remove items from your purchase history and that just might be illegal.
This may seem like an easy fix for the end user - us- the iTunes customer - but it just isn't practical for Apple to allow this to occur. In the real world, they just can't remove records for purchases which is what this would amount to.
Removing apps and app notifications from occurring may be a different issue, but I see no way that Apple can allow users to delete items from their purchase history.