So I go into my local Best Buy - purchase an iTunes Card and load it to my account. Now I can't use it how I want - to purchase what I want, or gift it as I see fit?
No, you can't. And that's common to many other stores as well, not to be able to buy gifts with a gift card. Why that is I don't know, but it's not unique to Apple.
I bought the itunes card with the specific intent of using it to gift apps, not realizing this policy was in place.
I guess you didn't read the back of the card. It says "Card may not be used to purchase any other merchandise, allowances, or iTunes gifting". It always pays to read the terms of any product to make sure it will meet your needs before you purchase.
If you have redeemed the card but not made any purchases from the balance, the iTunes Store may be able to put the credit "back" onto the card so you can sell or give it to someone else who can use it as is intended. Go here:
http://www.apple.com/support/itunes/contact/
and follow the instructions to contact the iTunes Store and make the request.
Regards.