Apple sells gift cards that can be redeemed online or in their physical stores. So far, so good.
Apple sells gift certificates for iTunes -- both phsycial and email versions. So far, so good.
A friend got me a $50 Apple Gift Card for Christmas. So far, awesome.
Apple won't allow my to use my Gift Card to buy songs off iTunes. Annoying.
Apple won't allow me to use my Gift Card to buy the email iTunes Gift Certificate (which I would receive immediately, and be able to use to buy the $50 worth of songs I've got saved in my iTunes cart, that I was planning on being able to listen to on the plane tomorrow).
Bastards.
Thinking about it, the reason behind it is probably either a) fraud prevention or b) the result of some legal settlement/contract along the way...but either way, it's incredibly crappy that I have credit with Apple, want to make a purchase, and can't through no fault of my own.
Apple, you suck. Fix this, because it makes iTunes and the Apple Music Store far less convenient. I don't really care what the underlying problem is; you're a smart company. Fix it and get out of the way of me spending money at your store.