Because it was invented some time in the 1940s. In the wake of what appears to be a global iTunes/App Store outage, Apple Store employees (at least those in the UK, where this picture was taken) are resorting to some severely old school methods of payment.
@brokenbottleboy Never thought I would see one of these old school card machines in the Apple Store in B'ham, UK!
Yes, that is a manual, carbon copy credit card imprinter. Or, for the kids out there, this thing:
The future! [The Next Web]