I've driven in Europe plenty of times, starting in the mid-80s on the German Autobahns especially, and never had an intentional driver license, but I agree that these days it's a good idea to carry one..simply for (as fjpikul wrote) to have it be the one the polizei decided to keep, instead of your regular license.
I've done the BMW European Delivery. Actually, they started it after my request in 1996. I was the editor-in-chief of Motor Trend at the time and thought it an interesting way to pick up our new 1997 540i Sport 6-speed test car. I ran it by BMW PR, and after a trip up the exec food chain, it came back with a "We've been considering starting a European delivery program. You can be first." It was a great deal, and the savings paid for much of the trip. Made the many tankfuls of $7/gallon (conversion rates back then) gasoline seem more palatable.
Here's the lead photo from the magazine article on that trip. That photo was shot "practical" (as they say in Hollywood), meaning no trickery or post-production. That was in the days of Kodachrome slide film, and before Photoshop existed. To get the shot without shadows on the gauges from the flash, I had to hold the camera upside down, while trying to steer, as the tach and speedometer needles both got to redline.
Amazing, also, is that there was a vacant autobahn in front of me. It was a weekday, somewhere away from Munich, and I just lucked out on traffic, weather, and getting the perfect shot.
This was redline in 5th gear, with one more cog to go. Fun times.
