Now I just think this is going to be an issue!
I thought having a backup of my wallet on USB and printing my private keys to a paper is safe
But apparently every time I spent, there is a new private key generated.
So I need to backup this new updated wallet and reprint my list of private keys.

Let's assume I made a paper wallet and transferred 1 BTC to it and gave it to my friend.
Then later, he spent 0.1 BTC on something by using the private key printed on that paper.
Little did he know, his wallet is now empty and useless, since there is 0.9 BTC change had been "refunded" to a different address with different private key.

The question is
Why does the transaction not give the change back to the same output address?