I never understood the lack of gift cards either. It makes no sense, I think a lot of people would love to get these as gifts. I know I would.
I do know, however, that my sister's fiancee wanted to help pay for her trip to PEK from YYZ about a year ago, and investigated a gift card from AC. He found out they didn't have them - the only alternative was to go to the airport, only to have a "gift certificate" literally written up on old paper ticket stock. This was for sure not redeemable online, and probably the most pathetic attempt at a gift certificate I have seen for a large corpporation. I understand this for an independent, mom and pop shop, but not for a major air carrier. Why they (and UA) still don't offer gift cards is beyond me.