Here's the thing. At Universal, you actually need to open up your wallet to spend money. Nobody does that anymore! In the 21st century, it's all about bands! Bands I tell you!
What guests want is to have to wear a bracelet during their entire vacation, hold it up against a monitor, be told the cashier wasn't ready, wait for them to do something, try again, maybe try a couple more times and then enter a PIN. Oh yeah, they have to make up and remember a PIN for the whole trip too. And then, sometimes the bands don't work. But it's soooooo much more convenient than carrying around cash or credit like people do every single day of their lives.
No one's going to want to deal with 20th century monetary exchanges at Universal when they can have magical transactions with the Mouse!