It seems that Bitcoin-Qt was created with the assumption that people would install it and use it. (Not play around with deleting some of its data files, moving pieces to other drives, and importing and exporting keys)
For the average user that expects to be able to send and receive money like they do with a bank account, it would only add confusion to show these "change" addresses. This is a protocol layer technical detail, and the wallet is designed to add a layer of abstraction so the user only needs to think about where they want to send the money, and how much they want to send (without needing to know all the intricate technical details about how such a transaction is handled at the protocol level).
Those who intend to use the software in advanced technical ways, are expected to know what they are doing.
As an alanogy: If I want to drive my car, I put the key in, turn it, move the lever to the "D" position and push the pedal near the floor. I don't need to understand gear ratios, compression ratios, fueal air mixtures, torque, valve timing, etc. If I decide that I want to play around with modfying valve timing, or replacing the fuel with an alternative fuel, then I'm expected to either understand fully what I am doing, or suffer the consequences.
Thanks for the helpful answers, but I don't agree your above analogy.
The bitcoin-qt client expects users to make backups of the wallet.dat file, it offers a 'backup wallet' option in the menu. So I would say it expects that this particular data file will be stored on other drives for future restoration.
There's nothing 'advanced' about restoring a backed up wallet file.
But there is no warning in the software that, as you've explained, any backup will only be good as long as it doesn't get older than 100 addresses/transactions behind the live wallet, after which any change the user receives will be going into addresses that the backup knows nothing about and can never access.
That means lost coins, possibly amounting to a huge sum of money, and there's no warning of that in the software. If bitcoin wants mass adoption and wants to be taken seriously for handling large sums, the official wallet client has to either show all the addresses coins are being stored in, so the user knows exactly where their money is, or it should warn (and warn in very big letters) that backups older than 100 transactions will lose some of your coins.