It's
1) the badge and
2) they have reached a point of evolution where they are pretty much trouncing everything else in their class and some of those in classes above.
But they are a victim of their own success as there are so many of them about.
I bet if I jumped in one and experienced the handling and balance all the reviewers mention is love one.
I will send him a message for you.
Ian and I test drove about 7 zeds 2 years at the wales meet to see the difference, I have to say of all of the that car pulled far better than the others, was a great little car and Ian loved it.