Gamerlord: Why don't they have them?
GorgorothX: Because gifting individual games is just more fun, and has better novelty.
Really, both options should be available. I kind of like the idea of being able to get a physical card good for one game here. It would be a lot more comfortable for me to give than to worry about getting the email address correct, when I could just pay to get it shipped to me.
Although, that's probably expensive enough to do that I don't see it as happening. More likely it would be a gift code, which would also be awesome as I wouldn't have to worry about them already owning the particular game.