I'll jump in here bc I don't think you're getting what people are saying, bradl. There are three types of authentication. (1) 4-digit passcode (2) iTunes Account Password (3) Touch ID...
Before Touch ID, you would use a 4-digit passcode (Method 1) to unlock the phone, then if you were to make a purchase, you would need to enter an iTunes Account Password (Method 2) as the added layer of protection/authentication for iTunes purchases.
Now, presumably, with Touch ID, you would be able to use Touch ID (Method 3) to unlock the phone, then it should prompt you to use Touch ID (Method 3) AGAIN to make purchases. What you are suggesting is that the use of the fingerprint to unlock the phone carries through to purchases, but that doesn't make sense. The unlocking of the phone and the authorization of purchases are two different acts.
What the OP is saying is that he/she is using Touch ID (Method 3) to unlock the phone, then being forced to use an iTunes Account Password (Method 2) to make iTunes purchases - which then renders Touch ID halfway useless for what it was advertised to be able to do (it should negate the need for typing in your iTunes Account Password)...
You are saying that by forcing a user to enter an iTunes Account Password (Method 2) even when they have Touch ID, it is an added layer of security. But it's not. It's stupid. You should be able to use Touch ID any time you need to enter a password - it is supposed to be a replacement for the need of a password.
I get that. What I don't think people are getting is the fact that if TouchID has already authenticated you into iTunes, and it does
NOT prompt you for any further authentication for purchases, once your phone is unlocked, any number of music or app purchases could be made directly to the phone and just pass through without any sort of controls on it.
Example: You use TouchID to unlock your phone, to give to Joey to play his favourite game.
Joey plays his game, closes it, then goes into iTunes looking for more apps.
Joey finds more apps that look cool to him, so he wants to get them.
Joey selects apps to download.
If TouchID has already unlocked your phone, it could have the potential to pass for your authentication into iTunes, allowing Joey to purchase any app he choses, no matter if it is free, or is $50.
That is why that second layer of authentication (the password) is handy here. It would prevent those purchases from happening, regardless of if TouchID passed that authentication to iTunes on the user's behalf or not.
If that is true, that second layer of authentication is a feature, as it is preventing erroneous app purchases to take place on your phone, saving you, Apple, and your payment processor heartburn in trying to get it all corrected.
BL.