A lot of it is management. Some of it is personality. In some cases the reputation is justified, and others it is not. It depends a lot on the strain.
There is certain advantages to birds that are active and alert, and when managed well, are a pleasure to own.
On a practical level they tend to be superior. More eggs, less feed, rustle up much of their own, better at getting away from a predator, etc. etc. They are certainly attractive to look at. Well bred examples are beautiful. The have a way about them that is difficult to describe.
I am sure that they are not for everyone. I am also sure that many that would appreciate them, and have an adequate setting for them, are missing out on something that they would really like.
They are not the little backyard chicken tractor kind of bird. They need some room to be active.
Personally, I have grown to appreciate the sharp style, alertness, and intelligence of the Mediterranean breeds. And I am speaking of them in general. It has been kind of an acquired taste for me. I was turned off by their reputation, until I tried them myself. Now I wonder what took me so long.
As far as handling, I am not picking up and petting my birds. They do not fit this model, but some could. I handle my birds off of the roost, where it is easier on me and the birds.
I am speaking of the Mediterranean breeds in general.