Forgive my ignorance, but wouldn't it be simpler to use your key to the world card so you don't have too many cards on you?
It's not ignorance, it's a matter of what people prefer. There are a LOT of people who don't want to open their wallets or bags or whatever and pull out a card.
Personally, I use regular Visa or Mastercard gift cards at all the booths. I could get a wrist thingy but I already have the cards so why bother? And yes, gift cards of any kind are accepted at the booths.
I dunno, seems to take the same amount of time at the registers so it's preferences rather than speed.