Yeah, but the point is WGT are needlessly depriving themselves of revenues that way.
I wouldn't permit the gifting of existing credits (such as those won in tournaments) either.
However, it's perfectly customary on web sites like Last.fm and hundreds of other well-run online businesses, to allow users to purchase subscriptions for someone else. Many newspapers' and magazines' websites offer the same thing ("gift subscriptions").
So, all that WGT needs to do is to insert a pop-up dialog with a question after a user presses the Purchase Credits button. The question would be: "Do you wish to purchase these credits for yourself or for another WGT user? If it is someone else, please fill in the name here."
That's it. There are no legal complications in this, no cheating or gambling possible, and WGT's cash flow would increase. It's mind-boggling why WGT don't allow this to happen.