I have read man resources and questions about HD Wallets. As pointed out in this question on SO, it won't be possible to send funds of a derived child address using the master private key.
In my humble opinion exactly this would make sense if I could create a derived child to receive funds for a specific purpose but being able to spend these funds using my master private key without the need to store each child private key.
Do I miss something here? Why should I use HD wallets if I still need to store each single local private key as well?