I remember being a bit let-down by the giraffes at Zoo Atlanta. I remember Columbia's Riverbanks Zoo's giraffes and they seemed so much taller to me there. I don't think there is a reasonable explanation because I can't really understand why unless none of these are fully-grown which I doubt.
But just like the zoo in Columbia, SC, Zoo Atlanta has a little area where you can trade the green in your billfold for green lettuce to feed the giraffe. I never had any interest doing it, but it was fun to watch other people give it a try.