Baerreis, DC is in fact the default. It's first in the list of payment types, it's pre-selected and worded in a way that makes it seem that it's the only way to pay with a credit card. There's no indication you can pay with a credit card through Paypal. Sellers are fooling themselves if they think this isn't the main reason they're seeing DC transactions.
So, I'm using it to give my customers another payment option, but I wish it wasn't designed so obviously to herd buyers into the DC corral.