I can’t be sure, but I think they actually have some kind of camera system that tags each order with a photo of the vehicle. I usually stop at McDs for my morning coffee, and I decided to pay for the person behind me all week for Christmas. So I told the guy taking my money that, and without looking away from his screen, he says"The white van?". So that’s my theory.
Now that I think of it, it could also be a good tool to deal with robbers, counterfeiters, pranksters, and the like. You could submit a photo of the car/driver/license plate to police along with timestamp of what they ordered and method of payment.
I never understood why Fast food restaurants cannot give me my food at the drive thru station #1 (cashier) if it is a relatively easy order.
I never order anything complicated, usually one of their top selling options, with no special requests. But many times I am stuck behind the van that has a $30 order. So I got to wait on them, while at station #1.
When I finally get to pull-up to Station #2, my order is bagged and ready to go, and I was stuck in line 4-5 minutes longer. If the cashier went up front and got my order ready, I could have been halfway home.