Still have my 1974 Ducati 750GT. But therein lies the difference: like a late 60's Ferrari, it's very street worthy today. It's smooth, fast (enough), handles well and (mine) is dead reliable. I don't have to go out and find a "retro" styled Ducati, the real (old) one works just fine. But like 60's Aston Martins, old English bikes are not wonderful on the road today. So, if you like those looks, the cool retros make sense. I'll keep my Ducati.
If evolution is outlawed only outlaws will evolve.