Why can't they do it properly? - Cars from 2000+ in scene from 1988..

In the last episode, when Barnum picks up a Taxi in Berlin, i believe it was 1988, we can the latest model of Mercedes E-Class and a BMW 3 Coupe. Both came just a few years ago. Why couldn't they make sure the shop cars from that era. These kind of things really ruins it for me?